CN209943443U

CN209943443U - Automatic tensioner with gas-liquid boosting cylinder

Info

Publication number: CN209943443U
Application number: CN201920285791.5U
Authority: CN
Inventors: 刘晓昂; 高中正
Original assignee: Hebei University of Technology
Current assignee: Hebei University of Technology
Priority date: 2019-03-07
Filing date: 2019-03-07
Publication date: 2020-01-14
Anticipated expiration: 2029-03-07

Abstract

The utility model discloses an automatic tensioner with a gas-liquid boosting cylinder, which comprises a gas-liquid boosting cylinder; the gas-liquid boosting cylinder comprises a cylinder body, a serial interface wall, an oil storage tank, a left part and a right part; the left part and the right part are symmetrically arranged in the cylinder body; a serial interface wall is fixed in the middle of the cylinder body; the serial interface wall is provided with a through hole which communicates the left part with the right part; two oil storage tanks are symmetrically arranged on the cylinder body; the oil storage tank comprises an oil storage tank body and an oil storage tank piston; the left part and the right part have the same structure and respectively comprise a sealing buffer block, a guide block, a piston rod, a hydraulic cylinder piston, a cylinder barrel serial interface wall, a pneumatic cylinder piston and a stop block; the pneumatic cylinder piston, the serial interface wall and the cylinder body form a pneumatic cylinder piston cavity, and gas is arranged in the pneumatic cylinder piston cavity. The tensioner takes the compressed air in the air chamber inserted into the piston cavity of the pneumatic cylinder through the piston of the pneumatic cylinder as the main buffering damper, and the damping basically does not attenuate along with the use time, thereby ensuring the stable work of the tensioner.

Description

Automatic tensioner with gas-liquid boosting cylinder

Technical Field

The utility model relates to a hydraulic equipment field specifically is an automatic tensioning ware with gas-liquid reinforcement jar.

Background

In order to achieve the goal of energy conservation and emission reduction, the automatic starting and stopping function of the automobile engine is gradually popularized. When the automobile with the automatic start-stop function is in a stop state, the engine stops working to save fuel oil; when the brake pedal is released, the engine will start again. To achieve rapid engine starting, the FEAD (Front End Accessory Drive) system used in an engine Accessory Drive system that incorporates an integrated starter motor/generator component requires two independent tensioners or an automatic tensioner that incorporates two tensioning arms to tension the belt, the latter being the dominant choice today.

The FEAD system generally includes a belt, a starter motor/generator pulley, a crankshaft pulley, a driven accessory pulley, a first tensioner pulley, and a second tensioner pulley. The starter motor/generator pulley, the crankshaft pulley, the driven accessory pulley, the first tensioner pulley and the second tensioner pulley are wound by using a belt. Because the FEAD system has different working modes, the tightness state of the belt is changed along with the mode conversion. The automatic tensioner is used as an important component of an FEAD system and mainly has the functions of maintaining the tension of belt sections at two ends of the automatic tensioner, increasing the wrap angle of an accessory wheel, compensating the change and attenuation of a belt caused by tension or abrasion, and compensating the swing of a tensioning arm caused by the fluctuation of the rotating speed of an engine, so that the belt is prevented from slipping, noise and vibration, the transmission level of the system is improved, and the normal operation of the system is ensured.

Currently available automatic tensioners are mainly of the friction type and of the hydraulic type. The friction type automatic tensioner adopts a damping piece (a spiral spring) to provide resistance and accumulate energy when the tight side arm contracts, provides power and releases energy when the loose side arm extends, and provides asymmetric damping for the tensioning arm under different working states by means of relative sliding of the damping piece and a surface in contact with the damping piece. Friction tensioners require a large installation space, while the damping member wears with operating time, resulting in damping attenuation and thus loss of efficiency. The hydraulic automatic tensioner generates damping by repeatedly compressing oil inside through the damping holes, and the damping effect is longer than that of friction type damping. But the damping device can generate large heat in the damping process and has heat influence on a hydraulic element (such as a one-way valve) for generating damping. The oil flows back and forth in the hydraulic elements, so that the hydraulic elements are abraded, and the hydraulic elements can be failed for a long time. The document of application No. 201410462258.3 discloses a hydraulic tensioner for belt accessories of an engine, which is a hydraulic tensioner widely used at present, and the structure divides the tensioner into an inner chamber and an outer chamber through a barrel, oil repeatedly flows in the inner chamber and the outer chamber through a gap between a plunger and the barrel or a check valve during the compression and the extension of the tensioner to generate damping, the inner chamber and the outer chamber are adopted, the radial size of the automatic tensioner is large, and the oil flowing out from the gap between the plunger and the barrel can cause the eccentricity of the plunger due to uneven pressure, and the service life of the tensioner is influenced.

SUMMERY OF THE UTILITY MODEL

To the deficiency of the prior art, the utility model aims to solve the technical problem of providing an automatic tensioner with a gas-liquid boosting cylinder.

The technical scheme of the utility model for solving the technical problems is to provide an automatic tensioner with a gas-liquid boosting cylinder, which is characterized in that the tensioner comprises a mounting bracket and the gas-liquid boosting cylinder; the gas-liquid boosting cylinder comprises a cylinder body, a serial interface wall, an oil storage tank, a left part and a right part; the cylinder body is fixed on a frame body of the FEAD system through a mounting bracket; the left part and the right part are symmetrically arranged in the cylinder body; a serial interface wall is fixed in the middle of the cylinder body; the serial interface wall is provided with a through hole which communicates the left part with the right part; two oil storage tanks are symmetrically arranged on the cylinder body; the oil storage tank comprises an oil storage tank body and an oil storage tank piston; the left part is connected with the first tensioner pulley, and the right part is connected with the second tensioner pulley; the left part and the right part have the same structure and respectively comprise a sealing buffer block, a guide block, a piston rod, a hydraulic cylinder piston, a cylinder barrel serial interface wall, a pneumatic cylinder piston and a stop block;

the cylinder barrel is connected with a boundary wall in series and is arranged in the cylinder body, and the left part of the cylinder barrel is provided with a hydraulic cylinder and a pneumatic cylinder; the sealing buffer block is in interference fit with the cylinder body and is arranged at the end part of the cylinder body; the guide block is in interference fit with the cylinder body and is tightly attached to the sealing buffer block; one end of the piston rod penetrates through the sealing buffer block and the guide block to extend out of the outer side of the cylinder body, the end part of the piston rod is fixedly provided with a tensioner pulley sleeve, the middle part of the piston rod is fixedly provided with a hydraulic cylinder piston, the piston rod penetrates through the cylinder barrel to be connected with a boundary wall in series, and the other end of the piston rod is fixedly provided with a pneumatic cylinder piston; the hydraulic cylinder piston is positioned in the hydraulic cylinder, and the pneumatic cylinder piston is positioned in the pneumatic cylinder; the tensioner pulley sleeve is arranged at the shaft end of the first tensioner pulley through a rolling bearing; the stop block is fixed on the serial interface wall; the pneumatic cylinder piston is in gapless fit with and pre-tightened with the stop block, and moves along the stop block; the oil storage tank body is fixed on the cylinder body, an oil storage tank piston is arranged in the oil storage tank body, and the oil storage tank is divided into an oil storage tank oil liquid cavity and an oil storage tank piston cavity; the piston cavity of the hydraulic cylinder is a cavity formed by the piston of the hydraulic cylinder, the cylinder barrel and the cylinder body which are connected in series with a boundary wall; the piston rod cavity of the pneumatic cylinder is a cavity formed by a pneumatic cylinder piston, a cylinder barrel, a serial interface wall and a cylinder body; the oil cavity of the oil storage tank is communicated with the piston cavity of the hydraulic cylinder through an oil through hole, and the piston cavity of the oil storage tank is communicated with the piston rod cavity of the pneumatic cylinder through an air vent; the pneumatic cylinder piston, the serial interface wall and the cylinder body form a pneumatic cylinder piston cavity, and gas is arranged in the pneumatic cylinder piston cavity.

Compared with the prior art, the utility model discloses beneficial effect lies in:

1. the tensioner inserts compressed air in the air buffer chamber through the pneumatic cylinder piston to serve as main buffering damping, the damping basically cannot be attenuated along with the use time, the compressed air cannot cause abrasion of working elements like oil liquid flowing, the stable work of the tensioner is guaranteed, and the swinging of a tensioning arm caused by the fluctuation of the rotating speed of an engine can be effectively attenuated on the whole.

2. The tensioner has two symmetrical tensioning arms, namely a loose edge arm and a tight edge arm, which can be matched with each other. When the FEAD system converts the working mode, the belt tightness states on two sides of the belt wheel of the starting motor/generator can be converted, and at the moment, the two tensioning arms can automatically make corresponding actions according to the belt tightness states: the tensioning arm (namely the tight side arm) at the tight side belt is compressed and fixed, and the tensioning arm (namely the loose side arm) at the loose side belt extends and tensions. Therefore, the belt is not continuously stretched due to frequent change of the working mode of the FEAD system, and the normal operation of the driving system is not influenced.

3. The utility model discloses a gas-liquid reinforcement jar replaces current coil spring. When the tight side arm contracts, the hydraulic cylinder piston and the pneumatic cylinder piston with certain damping and the resistance action of the squeezed oil and the gas in the gas buffer chamber provide damping and accumulate energy, and when the loose side arm extends, the power can be provided and the energy can be released through two modes of gas squeezing expansion and oil boosting. Even if the working time is too long, the spring will not be mechanically abraded like a spiral spring. In addition, when the spiral spring fails and needs to be replaced, the cylinder body can only be disassembled for replacement, which wastes time and labor. The gas-liquid booster cylinder can gradually dissipate the gas in the cylinder body because the cylinder body cannot be completely sealed, but the gas can be supplemented through a working hole (not shown in the figure) arranged on the cylinder body, so that the operation is convenient.

4. The tensioner can provide larger damping for the tight side arm through the resistance action of the liquid cylinder piston and the air cylinder piston with certain damping and the gas in the extruded oil and gas buffer chamber, and provide smaller damping for the loose side arm through the extruded gas in the liquid cylinder piston, the air cylinder piston and the air cylinder piston rod cavity with certain damping. Thus, the two tight arms can be properly damped under various motor modes, and the working effect of quickly tensioning and damping the belt vibration is achieved.

5. The tensioner may be installed on a FEAD system of a hybrid vehicle internal combustion engine with a reversible generator or a starter motor/generator. The gas-liquid booster cylinder can provide power for tensioning the piston rod and asymmetric damping required by the piston rod in different modes, and is long in service life.

Drawings

FIG. 1 is a layout diagram of a prior art FEAD system;

FIG. 2 is a transmission function diagram of a prior art FEAD system in generator mode;

FIG. 3 is a transmission function diagram of a prior art FEAD system in a starter motor mode;

fig. 4 is a schematic overall structure diagram of an embodiment of the present invention;

fig. 5 is a schematic view of a pneumatic cylinder piston according to an embodiment of the present invention;

fig. 6 is a schematic view of the installation of the guide block and the sealing buffer block according to an embodiment of the present invention;

in the figure: 1. a FEAD system; 2. a belt; 3. a crankshaft pulley; 4. a driven accessory wheel; 5. starting the motor/generator pulley; 6. a first tensioner pulley; 7. a second tensioner pulley; 8. mounting a bracket; 9. a piston rod cavity of the hydraulic cylinder; 10. a tensioner pulley sleeve; 11. sealing the buffer block; 12. a guide block; 13. a piston rod; 14. a hydraulic cylinder vent; 15. a hydraulic cylinder; 16. a hydraulic cylinder piston; 17. an oil through hole; 18. the cylinder barrel is connected with a boundary wall in series; 19. oil liquid; 20. an oil storage tank body; 21. an oil reservoir piston; 22. a vent; 23. a pneumatic cylinder; 24. a pneumatic cylinder piston; 25. a gas buffer chamber; 26. a stopper; 27. a serial interface wall; 28. a cylinder body; 29. a pneumatic cylinder piston chamber; 30. a piston rod cavity of the pneumatic cylinder; 31. an oil reservoir piston chamber; 32. an oil storage tank oil liquid cavity; 33. a piston cavity of the hydraulic cylinder.

Detailed Description

Specific embodiments of the present invention are given below. The specific embodiments are only used for further elaboration of the invention, and do not limit the scope of protection of the claims of the present application.

The FEAD system 1 (shown in fig. 1) includes a belt 2, a starter motor/generator pulley 5, a crankshaft pulley 3, a driven accessory pulley 4, a first tensioner pulley 6 and a second tensioner pulley 7. The starter motor/generator pulley 5, the crankshaft pulley 3, the driven accessory pulley 4, the first tensioner pulley 6 and the second tensioner pulley 7 are wound by using the belt 2.

The utility model provides an automatic tensioner (referred to as tensioner for short, see figures 4-6) with a gas-liquid boosting cylinder, which is characterized in that the tensioner comprises a mounting bracket 8 and a gas-liquid boosting cylinder; the gas-liquid booster cylinder comprises a cylinder body 28, a serial interface wall 27, an oil storage tank, a left part and a right part; the cylinder 28 is fixed on the frame body of the FEAD system 1 through the mounting bracket 8; the starting motor/generator belt wheel 5 is nested in the cylinder body 28, and the two do not contact; the left and right portions are symmetrically mounted inside the cylinder 28; a serial interface wall 27 is fixedly arranged in the middle of the cylinder body 28; the serial connection boundary wall 27 is provided with a through hole for communicating the left part with the right part; two oil storage tanks are symmetrically arranged on the cylinder body 28 left and right and are respectively positioned on the same positions of the left part and the right part; the oil storage tank comprises an oil storage tank body 20 and an oil storage tank piston 21; the left part is connected with a first tensioner pulley 6 and the right part is connected with a second tensioner pulley 7; the left part and the right part have the same structure and respectively comprise a sealing buffer block 11, a guide block 12, a piston rod 13, a hydraulic cylinder piston 16, a cylinder barrel serial interface wall 18, a pneumatic cylinder piston 24 and a stop block 26;

taking the left part as an example, the cylinder barrel serial connection boundary wall 18 is arranged inside the cylinder body 28, and the left part is a hydraulic cylinder 15 and a pneumatic cylinder 23; the sealing buffer block 11 is in interference fit with the cylinder body 28 and is arranged at the end part of the cylinder body 28; the guide block 12 is in interference fit with the cylinder body 28 and is tightly attached to the sealing buffer block 11; the guide block 12 is used for guiding and limiting the piston rod 13 to avoid the contact between the piston rod 13 and the cylinder body 28; one end of the piston rod 13 passes through the sealing buffer block 11 and the guide block 12 and extends out of the outer side of the cylinder body 28, the end part is fixed with a tensioner pulley sleeve 10, the middle part is fixed with a hydraulic cylinder piston 16, the piston passes through the cylinder barrel and is connected with a boundary wall 18 in series, and the other end is fixed with a pneumatic cylinder piston 24; the hydraulic cylinder piston 16 is located in the hydraulic cylinder 15, and the pneumatic cylinder piston 24 is located in the pneumatic cylinder 23; the tensioner pulley sleeve 10 is arranged at the shaft end of the first tensioner pulley 6 through a rolling bearing, and axial positioning is realized through a nut; the stop 26 is fixed on the serial connection interface wall 27; the pneumatic cylinder piston 24 is in gapless fit with the stop 26 and is pre-tightened, and the pneumatic cylinder piston 24 moves along the stop 26; the oil storage tank body 20 is fixed on the cylinder body 28, an oil storage tank piston 21 is arranged in the oil storage tank body, and the oil storage tank is divided into an oil storage tank oil liquid cavity 32 and an oil storage tank piston cavity 31; the piston cavity 33 of the hydraulic cylinder is a cavity formed by the piston 16 of the hydraulic cylinder, the cylinder barrel serial connection boundary wall 18 and the cylinder body 28; the pneumatic cylinder piston rod cavity 30 is a cavity formed by the pneumatic cylinder piston 24, the cylinder barrel serial connection boundary wall 18 and the cylinder body 28; the oil storage tank oil liquid cavity 32 is communicated with the hydraulic cylinder piston cavity 33 through the oil through hole 17, and the oil storage tank piston cavity 31 is communicated with the pneumatic cylinder piston rod cavity 30 through the air vent 22; the cylinder piston 24, the series interface wall 27 and the cylinder 28 form a cylinder piston chamber 29, the cylinder piston chamber 29 having a gas therein.

The cylinder piston 16, the guide block 12 and the cylinder block 28 form a cylinder piston rod chamber 9.

Preferably, the lower side of the hydraulic cylinder 15 is provided with a guide block 12 as the cylinder wall of the hydraulic cylinder 15, and a cylinder vent 14 connected to the outside is provided near the cylinder wall, so that the tensioning speed is not affected by the damping effect of the compressed gas in the piston rod chamber 9 of the hydraulic cylinder when the piston rod 13 is extended.

An even number of (preferably two) stoppers 26 are symmetrically arranged on both sides of the center line of the through hole of the serial connection boundary wall 27, and divide a pneumatic cylinder piston chamber 29 formed by the pneumatic cylinder piston 24, the serial connection boundary wall 27 and the cylinder body 28 into a plurality of independent gas buffer chambers 25 for gapless cooperation with the pneumatic cylinder piston 24 so that the pneumatic cylinder piston 24 can move in the gas buffer chambers 25.

The reservoir piston chamber 31 is a space having dry gas, and performs gas exchange with the cylinder rod chamber 30 as a gas capacity space. The tank oil chamber 32 is a chamber containing oil 19, and is a liquid volume space for exchanging liquid with the cylinder piston chamber 33.

Preferably, the guide block 12 is sleeved with a self-lubricating bearing, so that the friction of the piston rod 13 can be reduced, and the sliding is facilitated.

Preferably, the end of the sealing buffer block 11 contacting with the tensioner pulley sleeve 10 is an arc surface matching with the end surface of the tensioner pulley sleeve 10, so as to avoid direct contact between the tensioner pulley sleeve 10 and the cylinder 28; the sealing buffer block 11 is made of rubber, so that the impact force can be reduced, and the system noise is reduced.

Preferably, the piston rod 13 is arc-shaped; the pneumatic cylinder piston 24 has a number of grooves for a clearance-free fit with the stops 26, the number of grooves being the same as the number of stops 26. The hydraulic cylinder piston 16 is generally rectangular; the size of the liquid cylinder piston 16 is smaller than the air cylinder piston 24, the specific dimensions of the air cylinder piston 24 are related to the volume of the air cylinder 23 and the air buffer chamber 25, and the specific dimensions of the liquid cylinder piston 16 are related to the volume of the liquid cylinder 15.

Preferably, the cylinder 28 is a circular arc cylinder with a cylinder radian greater than a semicircle.

Preferably, the width of the liquid cylinder 15 is smaller than that of the air cylinder 23 because of the incompressibility of the liquid, and when the air in the air cylinder piston rod chamber 30 is discharged to the oil reservoir piston chamber 31, the volume of the discharged air is closer to the volume of the discharged oil 19 in the oil reservoir 20. If the pneumatic cylinder 23 and the hydraulic cylinder 15 are of the same width, the oil 19 discharged into the cylinder piston chamber 33 has difficulty in pushing the cylinder piston 16 in the hydraulic cylinder 15, so that the force-increasing effect is not achieved.

Preferably, a coil spring is passed through the through hole of the serial interface wall 27, and both ends are connected to the left and right pneumatic cylinder pistons 24, respectively. The spiral spring can assist and cooperate with the gas-liquid boosting cylinder to provide resistance for the contraction of the piston rod and assist for the extension of the piston rod, and the compression amount and the extension amount of the spiral spring can be reduced under the working condition of the gas-liquid boosting cylinder, so that the service life of the spring is prolonged.

Preferably, the center of the starter motor/generator pulley 5 coincides with the center of the present tensioner (see fig. 4).

The utility model discloses a theory of operation and work flow are:

when the FEAD system 1 is in the starter motor mode (see fig. 3), the starter motor/generator pulley 5 is in the starter motor pulley state and becomes the driving pulley, and the rotation direction is clockwise (clockwise in this embodiment). The belt 2 is driven by the driving wheel 5 to rotate, and the crankshaft belt wheel 3 and the driven accessory wheel 4 both serve as driven wheels to rotate clockwise. At this time, the belt where the second tensioner pulley 7 is located becomes loose, and the tensioner is required to stretch to compress the belt for tensioning; the belt in which the first tensioner pulley 6 is located is tightened and pressed, compressing the piston rod 13 in the left part, which is now the tight side arm. The oil 19 existing in the cylinder piston chamber 33 is pressurized and flows to the tank oil chamber 32 through the oil port 17, and the tank oil chamber 32 expands in volume to push the tank piston 21 to move in the expansion direction of the tank oil chamber 32, and pushes the gas in the tank piston chamber 31 to be discharged to the cylinder rod chamber 30 through the vent port 22. The tightness is such that oil 19 cannot pass the liquid cylinder piston 16 and gas cannot pass the gas cylinder piston 24. The piston rod 13 is subjected to the resistance of the hydraulic cylinder piston 16 and the pneumatic cylinder piston 24 with certain damping and the squeezed oil 19 and the gas in the gas buffer chamber 25 during the contraction process, and the contraction of the piston rod 13 is slowed down, so that the vibration of the tensioner is attenuated. At this time, the belt 2 at the second tensioner pulley 7 is a slack side at this time, and the right portion is a slack side arm, and the piston rod 13 is required to be extended to drive the second tensioner pulley 7 to be tensioned. Due to the contraction of the left piston rod 13, the gas present in the left pneumatic cylinder piston chamber 29 is pressurized and enters the right pneumatic cylinder piston chamber 29 through the through-hole of the serial interface wall 27, thereby pushing the right piston rod 13 to expand outward. At this time, the gas in the rod chamber 30 of the air cylinder is compressed and discharged to the piston chamber 31 of the oil reservoir, and the oil reservoir piston 21 is pushed to press the oil 19 in the oil reservoir chamber 32 to flow to the piston chamber 33 of the liquid cylinder. The oil 19 extrudes the hydraulic cylinder piston 16 to provide force reinforcement for the piston rod 13, so as to accelerate the stretching speed of the piston rod 13 and achieve the purpose of rapidly tensioning the belt at the right part.

When the FEAD system 1 is in the generator mode (see fig. 2), the crankshaft pulley 3 is a driving pulley at this time, the rotation direction is clockwise (clockwise in this embodiment), and the starter motor/generator pulley 5 is in the generator pulley state at this time. Under the drive of the belt 2, the driven accessory wheel 4 and the starting motor/generator belt wheel 5 both serve as driven wheels to rotate clockwise, at the moment, the belt where the first tensioner belt wheel 6 is located becomes loose, and the tensioner is required to stretch to compress the belt for tensioning; the belt on which the second tensioner pulley 7 is located is tightened and pressed, and the piston rod 13 at the right part is compressed, and at this time, the right part is a tight side arm. The oil 19 existing in the cylinder piston chamber 33 is pressurized and flows to the tank oil chamber 32 through the oil port 17, and the tank oil chamber 32 expands in volume to push the tank piston 21 to move in the expansion direction of the tank oil chamber 32, and pushes the gas in the tank piston chamber 31 to be discharged to the cylinder rod chamber 30 through the vent port 22. The tightness is such that oil 19 cannot pass the liquid cylinder piston 16 and gas cannot pass the gas cylinder piston 24. The piston rod 13 is subjected to the resistance of the hydraulic cylinder piston 16 and the pneumatic cylinder piston 24 with certain damping and the squeezed oil 19 and the gas in the gas buffer chamber 25 during the contraction process, and the contraction of the piston rod 13 is slowed down, so that the vibration of the tensioner is attenuated. At this time, for the left part of the tensioner, the belt 2 at the first tensioner pulley 6 is at this time slack side, and the left part is a slack side arm, and the piston rod 13 is required to be stretched to drive the first tensioner pulley 6 to be tensioned. Due to the contraction of the right piston rod 13, the gas present in the right pneumatic cylinder piston chamber 29 is pressurized and enters the left pneumatic cylinder piston chamber 29 through the through-holes of the serial interface wall 27, thereby pushing the left piston rod 13 to expand outward. At this time, the gas in the rod chamber 30 of the air cylinder is compressed and discharged to the piston chamber 31 of the oil reservoir, and the oil reservoir piston 21 is pushed to press the oil 19 in the oil reservoir chamber 32 to flow to the piston chamber 33 of the liquid cylinder. The oil 19 extrudes the hydraulic cylinder piston 16 to provide force reinforcement for the piston rod 13, so as to accelerate the stretching speed of the piston rod 13 and achieve the purpose of rapidly tensioning the belt at the left part.

Because tight edges occur and slack edges occur in each operating mode of the FEAD system, the operation of the left and right portions of the tensioner are correspondingly reversed. For example, when the left piston rod 13 is retracted, the corresponding right piston rod 13 is extended.

The utility model discloses the nothing is mentioned the part and is applicable to prior art.

Claims

1. An automatic tensioner with a gas-liquid boosting cylinder is characterized by comprising a mounting bracket and the gas-liquid boosting cylinder; the gas-liquid boosting cylinder comprises a cylinder body, a serial interface wall, an oil storage tank, a left part and a right part; the cylinder body is fixed on a frame body of the FEAD system through a mounting bracket; the left part and the right part are symmetrically arranged in the cylinder body; a serial interface wall is fixed in the middle of the cylinder body; the serial interface wall is provided with a through hole which communicates the left part with the right part; two oil storage tanks are symmetrically arranged on the cylinder body; the oil storage tank comprises an oil storage tank body and an oil storage tank piston; the left part is connected with the first tensioner pulley, and the right part is connected with the second tensioner pulley; the left part and the right part have the same structure and respectively comprise a sealing buffer block, a guide block, a piston rod, a hydraulic cylinder piston, a cylinder barrel serial interface wall, a pneumatic cylinder piston and a stop block;

2. The automatic tensioner as in claim 1, wherein the hydraulic cylinder piston, the guide block and the cylinder body define a hydraulic cylinder piston rod chamber.

3. The automatic tensioner as claimed in claim 2, wherein the lower side of the hydraulic cylinder is a cylinder wall of the hydraulic cylinder by a guide block, and a hydraulic cylinder vent connected to the outside is provided near the cylinder wall, so that the tensioning speed is not affected by the damping action of the compressed gas in the piston rod chamber of the hydraulic cylinder when the piston rod is extended.

4. The automatic tensioner as claimed in claim 1, wherein an even number of stoppers are symmetrically disposed on both sides of the center line of the through hole of the serial interface wall to divide the piston chamber of the pneumatic cylinder into a plurality of independent gas buffer chambers for fitting the piston of the pneumatic cylinder without a gap so that the piston of the pneumatic cylinder can move in the gas buffer chambers.

5. The automatic tensioner with a gas-liquid energizing cylinder according to claim 1, wherein the reservoir piston chamber is a space having dry gas as a gas capacity space for gas exchange with the piston rod chamber of the pneumatic cylinder; the oil cavity of the oil storage tank is a cavity with oil and is used as a liquid volume space for carrying out liquid exchange with the piston cavity of the hydraulic cylinder.

6. The automatic tensioner as claimed in claim 1, wherein the guide block has a self-lubricating bearing disposed therein to reduce friction of the piston rod for sliding movement.

7. The automatic tensioner with a gas-liquid boosting cylinder as claimed in claim 1, wherein the end of the sealing buffer block contacting with the tensioner pulley sleeve is a circular arc surface matching with the end surface of the tensioner pulley sleeve, so as to avoid direct contact between the tensioner pulley sleeve and the cylinder body; the sealing buffer block is made of rubber.

8. The automatic tensioner with a gas-liquid energizing cylinder according to claim 1, characterized in that preferably the piston rod is circular arc-shaped; the pneumatic cylinder piston is provided with a plurality of grooves which are in gapless fit with the stop blocks, and the number of the grooves is the same as that of the stop blocks; the size of the hydraulic cylinder piston is smaller than that of the pneumatic cylinder piston.

9. The automatic tensioner as claimed in claim 1, wherein the hydraulic cylinder is smaller in width than the pneumatic cylinder.

10. The automatic tensioner as claimed in claim 1, wherein the coil spring is inserted through the through hole of the serial interface wall, and both ends of the coil spring are connected to the left and right pneumatic cylinder pistons, respectively.