CN110925369B

CN110925369B - Timing chain tightener

Info

Publication number: CN110925369B
Application number: CN201911237198.4A
Authority: CN
Inventors: 李乾龙; 费侃; 戚俊维; 张莹; 赵乃博
Original assignee: Zhejiang Geely Holding Group Co Ltd; Ningbo Geely Royal Engine Components Co Ltd
Current assignee: Zhejiang Geely Holding Group Co Ltd; Ningbo Geely Royal Engine Components Co Ltd
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2020-12-18
Anticipated expiration: 2039-12-05
Also published as: CN110925369A

Abstract

The invention provides a timing chain tightener, and belongs to the technical field of engines. The problems that an existing engine is poor in NVH performance and unstable in chain tightener operation when started are solved. This tight chain ware in right time, including the casing that has the plunger chamber and set up the main plunger in the plunger intracavity, be equipped with the axially sliding's that can follow the main plunger in the main plunger secondary plunger, the main plunger is stretched out to the upper end of secondary plunger, the bottom in plunger chamber is equipped with the valve, the valve is cut apart into the plunger chamber main pressure room and is located the inferior pressure room of the top of valve, the main pressure room is located between oil duct and the inferior pressure room, the lower extreme of main plunger extends in the main pressure room, the lower extreme of secondary plunger is located the inferior pressure room. This structure has improved NVH performance and the stability of chain tightener during operation when engine starts.

Description

Timing chain tightener

Technical Field

The invention belongs to the technical field of automobile engines, and relates to a timing chain tightener.

Background

In the working process of the engine, four processes of air intake, compression, explosion and exhaust are continuously generated in a cylinder, the time of each step is matched with the motion state and position of a piston, the stroke of the piston, the opening and closing sequence of a valve and the ignition sequence are kept to be in 'synchronous' operation under the connection action of a 'timing mechanism', and each cylinder is enabled to exactly realize the following steps: when the piston is right up to the top dead center, the valve is right closed, and the spark plug is right ignited. The timing mechanism of the engine is an important component of an engine gas distribution system, the accuracy of gas inlet and exhaust time is ensured by connecting with a crankshaft and matching with a certain transmission ratio, the timing mechanism of the engine generally comprises accessories such as a timing chain, a chain tensioning rail, a timing chain tightener and the like, the timing chain tightener is communicated with an engine oil duct of the engine, and after the engine runs, the engine supplies engine oil to the timing chain tightener, so that the timing chain tightener pushes the chain tensioning rail to tighten the timing chain.

For example, chinese patent network discloses a timing chain transmission system of an engine [ grant publication No.: CN201496113U, including an air inlet sprocket, an air outlet sprocket, a timing sprocket and a timing chain wound around the above sprockets, wherein the timing chain is provided with an adjusting mechanism capable of adjusting the tension of the timing chain, the adjusting mechanism includes a chain tensioning rail in contact with the timing chain, the chain tensioning rail is provided with a chain tightener for controlling the chain tensioning rail to work, the chain tightener is communicated with the lubricant oil duct of the engine, the chain tightener draws oil from the lubricant oil duct of the engine, the lubricant oil flowing out from the oil outlet of the chain tightener is injected onto the timing chain to lubricate the timing chain during alignment, when the chain is loosened, the plug pin on the chain tightener is pulled out, and after the plug pin is pulled out, the plug on the chain tightener is ejected and acts on the end of the chain tensioning rail to tighten the timing chain, so that the timing chain keeps a certain tension and does not swing at will.

The timing chain transmission system has the following defects: 1. when the engine is in an initial working state, the rotation speed fluctuation of the engine is large, the oil pressure in an engine oil channel cannot be established, the oil pressure in the engine oil channel is low, and a sufficient power source cannot be provided for a chain tightener, so that the oil pressure of the chain tightener is insufficient, the chain tightener cannot keep a dynamic tensioning effect of a chain tensioning rail, the accuracy of gas distribution timing cannot be ensured, the problems that the engine and a chain system are abnormal, the engine vibrates and the like are caused, the NVH performance of the engine is reduced, and the comfort of the whole vehicle is influenced; 2. in the normal operation process of an engine, when an oil channel is blocked or an oil pipeline leaks oil, the oil pressure damping of the chain tightener is reduced, so that the tension provided by the chain tightener is reduced, the chain tightener fails, the chain tightener is damaged, the chain tightener loses the tensioning function, the plunger of the chain tightener is separated from the chain tensioning rail, the timing system of the engine is disordered, and the engine is scrapped.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a timing chain tightener, which aims to solve the technical problems that: how to improve NVH performance of an engine in an initial state while ensuring the stability of a chain tightener.

The purpose of the invention can be realized by the following technical scheme:

a timing chain tightener comprises a shell with a plunger cavity and a main plunger arranged in the plunger cavity, wherein an oil duct communicated with the lower end of the plunger cavity is formed in the shell, and the timing chain tightener is characterized in that a secondary plunger capable of sliding along the axial direction of the main plunger is arranged in the main plunger, the upper end of the secondary plunger extends out of the main plunger, a valve is arranged at the bottom of the plunger cavity and divides the plunger cavity into a main pressure chamber and a secondary pressure chamber positioned above the valve, the main pressure chamber is positioned below the secondary pressure chamber, the lower end of the main plunger extends into the main pressure chamber, the lower end of the secondary plunger is positioned in the secondary pressure chamber, when the oil pressure in the secondary pressure chamber is greater than the oil pressure in the oil duct, the valve controls the secondary pressure chamber to be communicated with the main pressure chamber and controls the oil duct to be disconnected with the main pressure chamber, and when the oil pressure in the secondary pressure chamber is less than the oil pressure in the oil, the valve controls the disconnection of the secondary pressure chamber from the primary pressure chamber and the communication of the control oil passage with the primary pressure chamber.

The working principle is as follows: the oil duct in the shell is communicated with an engine oil duct of an engine, in an initial state, the secondary pressure chamber is filled with engine oil, the secondary pressure chamber is not communicated with the main pressure chamber, the oil duct is not communicated with the main pressure chamber, the secondary plunger is contacted with the chain tensioning rail to provide tensioning force for the chain tensioning rail, when the engine is just started, the oil pressure in the oil duct is not established, the oil pressure in the secondary pressure chamber is larger than the oil pressure in the oil duct at the moment, the valve controls the secondary pressure chamber to be communicated with the main pressure chamber, the engine speed fluctuation is large, the crankshaft speed is not uniform, so that the chain tensioning rail vibrates, the secondary plunger floats up and down along with the vibration of the chain tensioning rail at the moment, the secondary plunger absorbs the vibration of the chain tensioning rail, the NVH of the engine at the initial starting stage and the comfort of a whole vehicle are improved, and the engine oil in the secondary pressure chamber, the engine oil in the primary pressure chamber flows out through a gap between the primary plunger and the shell and lubricates the chain tensioning rail, and the engine oil in the secondary pressure chamber flows out through a gap between the primary plunger and the secondary plunger and lubricates the chain tensioning rail; in the normal operation process of an engine, oil pressure in an oil duct is established, the oil pressure in the oil duct is larger than the oil pressure in a secondary pressure chamber, a valve controls the secondary pressure chamber to be not communicated with a main pressure chamber, a control oil duct is communicated with the main pressure chamber, high-pressure oil in the oil duct enters the main pressure chamber, a main plunger is pushed upwards by engine oil in the main pressure chamber, the main plunger and a secondary plunger are abutted against a chain tensioning rail at the same time, at the moment, if the oil duct of the engine oil is blocked or an oil pipeline leaks oil, the oil pressure in the main pressure chamber is reduced, so that the tensioning force provided by the main plunger is reduced, the main plunger is separated from the chain tensioning rail, but the secondary plunger is always in contact with the chain tensioning rail, the tensioning force is provided for the chain tensioning rail, the condition that a chain tightener fails is avoided.

In the timing chain tightener, the valve comprises a valve body, the upper end of the valve body is positioned in the lower end of the main plunger, the lower end of the valve body abuts against the bottom surface of the plunger cavity, the upper end of the valve body is provided with an upper oil inlet communicated with the secondary pressure chamber, the lower end of the valve body is provided with a lower oil inlet communicated with the oil duct, the side part of the valve body is provided with an oil drainage port communicated with the main pressure chamber, and a valve core assembly is arranged in the valve body; when the oil pressure in the secondary pressure chamber is greater than the oil pressure in the oil duct, the upper oil inlet is controlled by the valve core assembly to be opened and the lower oil inlet is controlled to be closed, and when the oil pressure in the secondary pressure chamber is less than the oil pressure in the oil duct, the upper oil inlet is controlled by the valve core assembly to be closed and the lower oil inlet is controlled to be opened.

Through the arrangement of the structure, when the engine is started, the valve core assembly controls the upper oil inlet to be opened and the lower oil inlet to be closed, the upper oil inlet is communicated with the valve body, the oil drainage port is communicated with the valve body, and high-pressure oil in the secondary pressure chamber sequentially passes through the upper oil inlet, the valve body and the oil drainage port to enter the primary pressure chamber; when the engine normally works, the lower oil inlet is controlled by the valve core assembly to be opened, the upper oil inlet is controlled by the upper oil inlet to be closed, the lower oil inlet is communicated with the valve body, the oil drainage port is communicated with the valve body, and high-pressure oil in the oil duct sequentially enters the main pressure chamber through the lower oil inlet, the valve body and the oil drainage port.

In foretell chain tightener in right time, the case subassembly is including setting up the last spheroid on valve body upper portion and setting up the lower spheroid in the valve body lower part, go up the spheroid and can open the oil inlet and make oil inlet and draining port be linked together on, the spheroid can open down the oil inlet and make oil inlet and draining port be linked together down, be equipped with the executor that can control spheroid and lower spheroid along upper and lower displacement respectively in the valve body.

By the device with the structure, in an initial state, the upper oil inlet is blocked by the upper ball body, the lower oil inlet is blocked by the lower ball body, and when the engine is started, the actuator drives the upper ball body to move downwards so that the upper oil inlet is in an open state; when the engine runs to a normal state, the actuator drives the upper ball body to move upwards, so that the upper oil inlet is in a closed state, and the actuator drives the lower ball body to move upwards, so that the lower oil inlet is in an open state.

In foretell chain tightener in right time, the executor includes ECU, is located the coil between spheroid and the lower spheroid, is located the spring one between spheroid and the lower spheroid, monitors the indoor oil pressure of secondary pressure and the interior oil pressure of oil duct and can give ECU's pressure sensor with two oil pressure signal transmission, the upper end and the last spheroid of coil are connected, the lower extreme is connected with lower spheroid, the coil is connected with ECU electricity, upward spheroid and lower spheroid can vertical displacement relatively when the coil circular telegram.

Through the arrangement of the structure, the pressure sensor respectively monitors the oil pressure of the secondary pressure chamber and the oil duct, the two monitored oil pressure signals are transmitted to the ECU, the ECU compares the two oil pressure signals, when the oil pressure in the secondary pressure chamber is greater than the oil pressure in the oil duct, the ECU controls the coil to be electrified, the coil drives the upper ball body to move downwards and the lower ball body to move downwards after being electrified, so that the upper ball body opens the upper oil inlet, and the lower ball body blocks the lower oil inlet; when the oil pressure in the secondary pressure chamber is smaller than the oil pressure in the oil duct, the ECU controls the coil to be electrified reversely, and the coil drives the upper ball body to move upwards and the lower ball body to move upwards after being electrified reversely, so that the upper ball body blocks the upper oil inlet, and the lower ball body opens the lower oil inlet; when no current passes through the coil, the upper ball body and the lower ball body are under the action of the first spring, so that the upper ball body is blocked by the upper oil inlet, and the lower ball body is blocked by the lower oil inlet. In this structure, ECU is through the electric current that increases or reduces the coil and change the current direction to the spheroid and lower spheroid position are gone up in the change, the aperture of oil inlet and lower oil inlet is gone up in the regulation.

In the timing chain tightener, the oil drain port is formed in both the side part of the upper end of the valve body and the side part of the lower end of the valve body.

Through the arrangement of the structure, after the upper oil inlet is opened, high-pressure oil in the secondary pressure cavity enters the main pressure cavity through the upper oil inlet, the valve body and the oil drainage port on the side part of the upper end of the valve body, so that the high-pressure oil in the secondary pressure cavity quickly enters the main pressure cavity; after the lower oil inlet is opened, high-pressure oil of the oil duct enters the main pressure cavity through the lower oil inlet, the valve body and an oil drainage port on the side part of the lower end of the valve body, so that the high-pressure oil in the oil duct quickly enters the main pressure cavity.

In the timing chain tightener, a second spring is arranged in the secondary pressure chamber, the upper end of the second spring abuts against the secondary plunger, and the lower end of the second spring abuts against the valve.

Through the setting of this structure, spring two makes secondary plunger have the trend of rebound all the time, and when the starter just started, spring two made secondary plunger can float from top to bottom along with the vibrations of chain tensioning rail.

In the timing chain tightener, a boss I is arranged on the inner side wall of the upper end of the main plunger, a boss II is arranged on the outer side wall of the lower end of the secondary plunger, a spring III is arranged between the boss I and the boss II, the upper end of the spring III is connected with the boss I, and the lower end of the spring III is connected with the boss II.

Through the arrangement of the structure, when the engine normally runs, the main plunger overcomes the acting force of the third spring to move upwards under the action of high-pressure oil in the main pressure chamber, so that the main plunger and the secondary plunger are both contacted with the chain tensioning rail, and when the engine is stopped, the third spring enables the main plunger to move downwards to reset. Under the condition, the force of the spring III driving the main plunger to move downwards and reset can be slightly larger than 0, and when the engine runs normally, the spring III always has the tendency of pulling the main plunger downwards, the jacking pressure of the main plunger on the chain tensioning rail is reduced, the stress of the chain tensioning rail is reduced, the fatigue requirement of the chain during alignment is further reduced, the risk of chain elongation is reduced, the service life of the timing chain is prolonged, the reliability of the engine is improved, 19-step squeal generated by a chain system can be improved, the NVH of the engine is improved, and the comfort of the whole vehicle is provided.

In foretell chain tightener in right time, this chain tightener in right time still includes pin and the couple of setting on the casing, the pin is worn to establish on the couple and through couple vertical spacing, the pin can remove along the horizontal direction, the pinhole has been seted up on the lateral wall of main plunger upper end, the one end of pin can be inserted in the pinhole.

Through the arrangement of the structure, when the engine is started, the pin moves along the horizontal direction to enable the pin to be pulled out of the pin hole, and the pin relieves the limitation on the main plunger piston, so that the main plunger piston can move upwards.

Compared with the prior art, this tight chain ware in right time has following advantage:

1. the secondary plunger of this structure floats from top to bottom along with the vibrations of chain tensioning rail, the vibrations of chain tensioning rail are absorbed to secondary plunger, improve the travelling comfort of starting initial engine NVH and whole car, and secondary plunger is at the in-process that floats from top to bottom, the indoor machine oil of secondary pressure flows into the main pressure room, the indoor machine oil of main pressure flows out and for chain tensioning rail lubrication through the clearance between main plunger and the casing, the indoor machine oil of secondary pressure flows out and for chain tensioning rail lubrication through the clearance between main plunger and the secondary plunger.

2. The secondary plunger is always in contact with the chain tensioning rail, so that tensioning force is provided for the chain tensioning rail, the condition that the chain tightener fails is avoided, and the use stability of the chain tightener is improved.

Drawings

FIG. 1 is a schematic sectional view of the timing chain tensioner.

FIG. 2 is a second schematic sectional view of the timing chain tensioner.

Fig. 3 is a partially enlarged view of a portion a in fig. 1.

Fig. 4 is a flowchart of the present timing chain tensioner.

In the figure, 1, a housing; 11. a plunger cavity; 2. a main plunger; 21. a first boss; 22. a pin hole; 3. an oil passage; 4. a secondary plunger; 41. a second boss; 5. a valve; 51. a valve body; 511. an upper oil inlet; 512. a lower oil inlet; 513. an oil drainage port; 52. a valve core assembly; 521. an upper sphere; 522. a lower sphere; 523. an actuator; 5231. a coil; 5232. a first spring; 5233. a pressure sensor; 6. a primary pressure chamber; 7. a secondary pressure chamber; 8. a second spring; 9. a third spring; 10. a pin; 12. and (4) hanging hooks.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

As shown in fig. 1-4, the timing chain tightener comprises a housing 1 having a plunger cavity 11 and a main plunger 2 disposed in the plunger cavity 11, wherein an oil passage 3 communicated with the lower end of the plunger cavity 11 is formed in the housing 1, a secondary plunger 4 capable of sliding along the axial direction of the main plunger 2 is disposed in the main plunger 2, the upper end of the secondary plunger 4 extends out of the main plunger 2, a valve 5 is disposed at the bottom of the plunger cavity 11, the plunger cavity 11 is divided into a main pressure chamber 6 and a secondary pressure chamber 7 disposed above the valve 5 by the valve 5, the main pressure chamber 6 is disposed below the secondary pressure chamber 7, the lower end of the main plunger 2 extends into the main pressure chamber 6, the lower end of the secondary plunger 4 is disposed in the secondary pressure chamber 7, a second spring 8 is disposed in the secondary pressure chamber 7, the upper end of the second spring 8 abuts against the secondary plunger 4, the lower end abuts against the valve 5, a first boss 21 is disposed on the inner side wall of, the outer side wall of the lower end of the secondary plunger 4 is provided with a second boss 41, a third spring 9 is arranged between the first boss 21 and the second boss 41, the upper end of the third spring 9 is connected with the first boss 21, and the lower end of the third spring is connected with the second boss 41.

As shown in fig. 1 and 2, the valve 5 includes a valve body 51, an upper end of the valve body 51 is located in a lower end of the main plunger 2, a lower end of the valve body 51 abuts against a bottom surface of the plunger cavity 11, an upper oil inlet 511 communicating with the secondary pressure chamber 7 is formed in the upper end of the valve body 51, a lower oil inlet 512 communicating with the oil passage 3 is formed in the lower end of the valve body 51, and oil drain openings 513 are formed in both a side portion of the upper end of the valve body 51 and a side portion. A valve core assembly 52 is arranged in the valve body 51, the valve core assembly 52 comprises an upper ball 521 arranged at the upper part of the valve body 51 and a lower ball 522 arranged at the lower part of the valve body 51, the upper ball 521 can open the upper oil inlet 511 to communicate the upper oil inlet 511 with the oil drain 513, the lower ball body 522 can open the lower oil inlet 512 to enable the lower oil inlet 512 to be communicated with the oil drain 513, an actuator 523 which can respectively control the upper ball body 521 and the lower ball body 522 to move up and down is arranged in the valve body 51, the actuator 523 comprises an ECU, a coil 5231 which is positioned between the upper ball body 521 and the lower ball body 522, a first spring 5232 which is positioned between the upper ball body 521 and the lower ball body 522, and a pressure sensor 5233 which monitors the oil pressure in the secondary pressure chamber 7 and the oil pressure in the oil passage 3 and can transmit two oil pressure signals to the ECU, the upper end of the coil 5231 is connected with the upper ball body 521, the lower end of the coil 5231 is connected with the lower ball body 522, the coil 5231 is electrically connected with the ECU, and the coil 5231.

The oil duct 3 in the shell 1 is communicated with an engine oil duct of an engine, in an initial state, the secondary pressure chamber 7 is filled with engine oil, the upper oil inlet 511 and the lower oil inlet 512 are both in a closed state, the secondary plunger 4 is in contact with a chain tensioning rail to provide tensioning force for the chain tensioning rail, when the engine is just started, oil pressure in the oil duct 3 is not established, the pressure sensor 5233 respectively monitors oil pressure of the secondary pressure chamber 7 and the oil duct 4, two monitored oil pressure signals are transmitted to the ECU, the ECU compares the two oil pressure signals, when the oil pressure in the secondary pressure chamber 7 is greater than the oil pressure in the oil duct 4, the ECU controls the coil to be electrified, the coil drives the upper ball 521 to move downwards to open the upper oil inlet 511, high-pressure oil in the secondary pressure chamber 7 flows into the main pressure chamber 6 through the upper oil inlet 511, the valve body 51 and the oil drain 513, the engine speed fluctuation is large, and the crankshaft, the chain tensioning rail is vibrated, the secondary plunger 4 floats up and down along with the vibration of the chain tensioning rail under the action of high-pressure oil in the secondary pressure chamber 7 and the spring II 8 at the moment, the secondary plunger 4 absorbs the vibration of the chain tensioning rail to improve the NVH of an engine at the initial starting stage and the comfort of a whole vehicle, in the process of floating up and down of the secondary plunger 4, engine oil in the secondary pressure chamber 7 flows into the main pressure chamber 6, the engine oil in the main pressure chamber 6 flows out through a gap between the main plunger 2 and the shell 1 and lubricates the chain tensioning rail, and the engine oil in the secondary pressure chamber 7 flows out through a gap between the main plunger 2 and the secondary plunger 4 and lubricates the chain tensioning rail; in the normal operation process of the engine, the oil pressure in the oil duct 3 is established, when the oil pressure in the secondary pressure chamber 7 is smaller than the oil pressure in the oil duct 3, the ECU controls the coil to be reversely electrified, the coil drives the upper ball 521 and the lower ball 522 to both move upwards to close the upper oil inlet 511 and open the lower oil inlet 512, the high-pressure oil in the oil duct 3 flows into the main pressure chamber 6 through the lower oil inlet 512, the valve body 51 and the oil drain 513, the main plunger 2 overcomes the acting force of the spring III 9 to move upwards under the action of the high-pressure oil in the main pressure chamber 6, the engine oil in the main pressure chamber 6 pushes the main plunger 2 upwards, the main plunger 2 and the secondary plunger 4 simultaneously abut against the chain tensioning rail, at the moment, when the oil duct is blocked or the oil leakage occurs in the engine oil duct, the oil pressure in the main pressure chamber 6 is reduced, so that the tensioning force provided by the main plunger 2 is reduced to separate, however, the secondary plunger 4 is always in contact with the chain tensioning rail to provide tensioning force for the chain tensioning rail, failure of the chain tightener is avoided, the use stability of the chain tightener is improved, meanwhile, the spring III 9 always has the tendency of pulling the main plunger 2 downwards, the jacking force of the main plunger 2 to the chain tensioning rail is reduced, the stress of the chain tensioning rail is reduced, the fatigue requirement of the chain during alignment is further reduced, the chain stretching risk is reduced, the service life of the timing chain is prolonged, the reliability of the engine is improved, 19-step squeal generated by a chain system can be improved, the NVH of the engine is improved, and the whole vehicle comfort is provided.

As shown in fig. 1, the timing chain tightener further comprises a pin 10 and a hook 12 arranged on the housing 1, the pin 10 penetrates through the hook 12 and is vertically limited through the hook 12, the pin 10 can move in the horizontal direction, a pin hole 22 is formed in the outer side wall of the upper end of the main plunger 2, and one end of the pin 10 can be inserted into the pin hole 22.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. The timing chain tightener comprises a shell (1) with a plunger cavity (11) and a main plunger (2) arranged in the plunger cavity (11), wherein an oil duct (3) communicated with the lower end of the plunger cavity (11) is formed in the shell (1), and is characterized in that a secondary plunger (4) capable of sliding along the axial direction of the main plunger (2) is arranged in the main plunger (2), the upper end of the secondary plunger (4) extends out of the main plunger (2), a valve (5) is arranged at the bottom of the plunger cavity (11), the plunger cavity (11) is divided into a main pressure chamber (6) and a secondary pressure chamber (7) located above the valve (5) by the valve (5), the main pressure chamber (6) is located below the secondary pressure chamber (7), the lower end of the main plunger (2) extends into the main pressure chamber (6), and the lower end of the secondary plunger (4) is located in the secondary pressure chamber (7), a second spring (8) is arranged in the secondary pressure chamber (7), the upper end of the second spring (8) is abutted against the secondary plunger (4), and the lower end of the second spring is abutted against the valve (5); when the oil pressure in the secondary pressure chamber (7) is larger than the oil pressure in the oil duct (3), the valve (5) controls the secondary pressure chamber (7) to be communicated with the main pressure chamber (6) and controls the oil duct (3) to be disconnected from the main pressure chamber (6), and when the oil pressure in the secondary pressure chamber (7) is smaller than the oil pressure in the oil duct (3), the valve (5) controls the secondary pressure chamber (7) to be disconnected from the main pressure chamber (6) and controls the oil duct (3) to be communicated with the main pressure chamber (6).

2. The timing chain tightener of claim 1, characterized in that the valve (5) comprises a valve body (51), the upper end of the valve body (51) is located in the lower end of the main plunger (2), the lower end of the valve body (51) abuts against the bottom surface of the plunger cavity (11), the upper end of the valve body (51) is provided with an upper oil inlet (511) communicated with the secondary pressure chamber (7), the lower end of the valve body (51) is provided with a lower oil inlet (512) communicated with the oil duct (3), the side of the valve body (51) is provided with an oil drain (513) communicated with the primary pressure chamber (6), and a valve core assembly (52) is arranged in the valve body (51); when the oil pressure in the secondary pressure chamber (7) is greater than the oil pressure in the oil duct (3), the valve core assembly (52) controls the upper oil inlet (511) to be opened and controls the lower oil inlet (512) to be closed, and when the oil pressure in the secondary pressure chamber (7) is less than the oil pressure in the oil duct (3), the valve core assembly (52) controls the upper oil inlet (511) to be closed and controls the lower oil inlet (512) to be opened.

3. The timing chain tensioner according to claim 2, wherein the valve core assembly (52) comprises an upper ball body (521) arranged at the upper part of the valve body (51) and a lower ball body (522) arranged at the lower part of the valve body (51), the upper ball body (521) can open the upper oil inlet (511) to enable the upper oil inlet (511) to be communicated with the oil drain port (513), the lower ball body (522) can open the lower oil inlet (512) to enable the lower oil inlet (512) to be communicated with the oil drain port (513), and an actuator (523) capable of respectively controlling the upper ball body (521) and the lower ball body (522) to move up and down is arranged in the valve body (51).

4. A timing chain tensioner according to claim 3, characterized in that said actuator (523) comprises an ECU, a coil (5231) between the upper sphere (521) and the lower sphere (522), a first spring (5232) between the upper sphere (521) and the lower sphere (522), a pressure sensor (5233) monitoring the oil pressure in the secondary pressure chamber (7) and the oil pressure in the oil passage (3) and being able to deliver two oil pressure signals to the ECU, said coil (5231) being connected at its upper end to the upper sphere (521) and at its lower end to the lower sphere (522), said coil (5231) being electrically connected to the ECU, said upper sphere (521) and said lower sphere (522) being able to displace relatively vertically when said coil (5231) is energized.

5. A timing chain tensioner according to claim 2, 3 or 4, characterized in that the side of the upper end of the valve body (51) and the side of the lower end of the valve body (51) are provided with the above-mentioned oil drain port (513).

6. The timing chain tightener of claim 1, 2, 3 or 4, characterized in that the inner side wall of the upper end of the main plunger (2) has a first boss (21), the outer side wall of the lower end of the secondary plunger (4) has a second boss (41), a third spring (9) is arranged between the first boss (21) and the second boss (41), the upper end of the third spring (9) is connected with the first boss (21), and the lower end is connected with the second boss (41).

7. The timing chain tightener of claim 6, characterized in that, the timing chain tightener further comprises a pin (10) and a hook (12) arranged on the housing (1), the pin (10) is arranged on the hook (12) in a penetrating manner and vertically limited through the hook (12), the pin (10) can move along the horizontal direction, a pin hole (22) is formed on the outer side wall of the upper end of the main plunger (2), and one end of the pin (10) can be inserted into the pin hole (22).