DE102006016494A1 - Hydraulic tension jack for belt or chain under tension in automotive engine has a wear-resistant valve seat surface - Google Patents

Abstract

A hydraulic tension jack holds a belt or chain under tension and is applied to a valve. The valve seat has a wear-resistant film that is a mixture of chrome, dichromonitride Cr2N and a monochromonitride CrN.

Description

BACKGROUND THE INVENTION

The The invention relates to a hydraulic tensioner which is used about the tension in a belt or chain for driving a camshaft to keep constant.

typically, contains a hydraulic tensioner a hydraulic damper, the variable loads wearing, which are exerted by a belt or a chain to vibrations of the belt or chain. The hydraulic damper has a check valve or check valve, that has a blocking ball that's for it is designed to be in and out of contact to move with the valve seat. When a pushing load to the hydraulic damper is applied, the blocking ball comes into contact with the valve seat, whereby the Pressure chamber is sealed, causing a flow of hydraulic Prevents fluid that fills the pressure chamber.

With Such a hydraulic tensioner are variable loads on the hydraulic damper created with a high frequency, which causes that the shut-off valve repeatedly opened at short intervals and is closed. Therefore, measures have been taken, the wear resistance of both the locking ball and the valve seat surface respectively to improve each other when touching each other the check valve closes. In particular, the blocking ball is made of a bearing steel and will harden subjected. The valve seat area is made of malleable steel alloy for machine shape use, for example, a steel for Carburizing, which contains a chromium steel and chromium molybdenum steel, and becomes a carburizing and a hardening subjected.

But usually tends the valve seat surface, which touches the locking ball in the same place, to wear off faster as the locking ball, which the seat at different points touched, as she turns. The wear of the valve seat surface causes Malfunction of the check valve, for example, a failure, the prevents hydraulic oil flows, or, for example, that the blocking ball does not separate from the valve seat surface, whereby the life of the hydraulic tensioner is shortened.

Around to solve this problem, Japanese Patent Publication 2002-357250A discloses a hydraulic tensioner, which has a valve seat surface with a hard Film or a hard layer of TiN or a diamond-like Carbon film (DLC film) is coated to the hardness of the Valve seat to increase.

If the valve seat, however, with a hard film of TiN or a DLC film However, the film itself may be the blocking ball as the touch part because of its high hardness rub. When the touch section a low surface roughness has, can the valve seat area even be damaged by protruding sections. Another Problem is the bad adhesion on the base metal due to the fact that the difference in the Hardness over the Base metal is big.

A Object of the present invention is a wear resistance the valve seat surface of the check valve to improve and thereby the life of a hydraulic tensioner to increase and to adapt the hydraulic tensioner to high loads.

OVERVIEW OF THE INVENTION

According to the present invention, there is provided a hydraulic tensioner comprising a cylinder filled with a hydraulic oil, a piston slidably mounted in the cylinder to divide the interior of the cylinder into a pressure chamber and a storage chamber, a linkage and a cylinder, respectively a push rod mounted in the cylinder for axial movement with the piston and having a free end protruding from the cylinder, a spring mounted in the cylinder and supporting the piston and the push rod is biased outwardly from the cylinder, the piston defining a passageway through which the pressure chamber is connected to the reservoir chamber and a check ball, ball valve, which is adapted to be in contact with a valve seat surface which is formed on a surface of the channel, whereby the channel is closed when the pressure in the Dr is higher than the pressure in the storage chamber, and is otherwise designed to be separated from the valve seat surface, wherein the valve seat surface is coated with a wear resistant composite film comprising a mixture of metallic chromium, dichromomononitrile Cr ₂ N and monochrome mononitride CrN.

According to a further aspect of the present invention, there is provided a hydraulic tensioner comprising a cylinder filled with a hydraulic oil, a piston movably disposed in the cylinder he can divide the interior of the cylinder into a pressure chamber and a storage chamber, a push rod which is arranged in the cylinder so that it can move axially with the piston, and which has a free end which protrudes from the cylinder, a spring, which is mounted in the cylinder and biases the piston and the push rod outwardly from the cylinder, the piston defining a channel through which the pressure chamber is connected to the storage chamber and having a ball valve or ball designed for it is to remain in contact with a valve seat surface which is formed on the surface of the channel, whereby the channel is closed when the pressure in the pressure chamber is higher than the pressure in the storage chamber, and otherwise designed to be separated from the valve seat surface in which the valve seat surface is coated with a wear-resistant composite film comprising a mixture of a metallic chromium and a monochrome mononitride CrN.

Prefers becomes the seat subjected to a lapping, before it is coated with the wear-resistant film, or the surface of the wear-resistant film is subjected to lapping after the Valve seat has been coated with the wear-resistant film to keep it smoother of the wear-resistant film. This makes it possible to prevent the wear-resistant film from being damaged, and to provide a hydraulic tensioner for use under high load conditions.

The entire valve seat surface is also preferably subjected to shot peening before coming up with the wear-resistant film is coated, or the surface of the Abnutzungsfesten film is subjected to shot peening after the valve seat surface with a wear-resistant film has been coated to the load resistance or resistance the wear-resistant film or the base metal of the piston improve. this makes possible it to provide a hydraulic tensioner, which is the use under high load conditions.

By Coating the valve seat surface with wear-resistant film, mainly metallic chrome and Chromium nitride, it is possible the wear of the valve seat surface because the wear-resistant film has excellent wear resistance or wear resistance, adhesiveness and hardness Has. this makes possible it to extend the life span of the hydraulic tensioner and to allow use under a heavy load.

SUMMARY THE DRAWINGS

1 Fig. 10 is a vertical front sectional view of a hydraulic tensioner embodying the present invention;

2 is an enlarged sectional view of a check valve of the hydraulic tensioner of 1 ;

3A to 3C are graphs showing the results of abrasion tests for the valve seat surface of the check valves; and

4 Fig. 10 is a vertical sectional view of a hydraulic tensioner according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. As in 1 and 2 1, the hydraulic tensioner embodying the present invention includes a cylinder 1 , which is a tubular part 1a which is made of an aluminum alloy and which has a closed bottom, and a valve sleeve 1b , which is made of a steel and in the pipe part 1a is inserted at the bottom. The cylinder 1 is filled with a hydraulic oil.

A piston 2 is in the cylinder 1 mounted such that it along an inner wall of the valve sleeve 1b can slide or move. A push bar 4 is with her lower end in a hole 3 inserted in the upper surface of the piston 2 is trained.

The push bar 4 extends slidably through a sealing member 5 , for example, an oil seal, which is the top opening of the cylinder 1 seals, and its upper end is outside the cylinder 1 ,

A wear ring 6 is on the push bar 4 mounted so that it along the inner wall of the pipe part 1a can slide and is by a spring 7 against a shoulder 4a pressed on the outer circumference of the push bar 4 is trained. The push bar 4 thus becomes outward of the cylinder 1 through the spring 7 biased. The piston 2 is against the bottom end of the push bar 4 pressed by a piston spring.

A pressure chamber 9 is under the piston 2 demarcated and a pantry 10 is above that piston 2 demarcated. The piston 2 is with a channel 11 formed by the pressure chamber 9 with the pantry 10 connected is. A check valve 12 or check valve is at the opening of the channel 11 the pressure chamber 9 provided facing.

The check valve 12 contains a blocking ball 14 , which is designed to be in or out of contact with the valve seat surface 13 to move at the bottom end of the channel 11 is formed, and a lock 15 that the movement of the blocking ball 14 limited and thus the degree of opening of the check valve 12 , When the pressure in the pressure chamber 9 about the pressure in the pantry 10 rises, the check valve closes 12 the channel 11 ,

When a camshaft drive belt (not shown) vibrates on the camshaft due to the fluctuating loads and the tension in the belt increases, the push bar becomes 4 in the cylinder 1 pushed. This causes the locking ball 14 seated on the seat, eliminating the channel 11 is closed. In this state, the hydraulic oil is used in the pressure chamber 9 for damping the compressive force acting on the push bar 4 attacks.

When the pushing or pushing force is the sum of the force of the spring 7 and the force of the piston spring 8th exceeds, hydraulic oil enters the pressure chamber 9 through a gap between the inner wall of the valve sleeve 1b and the piston 2 in the pantry 10 out, which allows the piston 2 slowly moves down until the pressing force with the sum of the force of the spring 7 and the force of the piston spring 8th is balanced, whereby the tension in the belt is kept constant.

When the belt slackens or is loose, the piston will move 2 and the push bar 4 quickly outward under the common force of the spring 7 and the piston spring 8th , As soon as the piston 2 and the push bar 4 As the movement begins, the pressure in the pressure chamber drops 9 below the pressure in the pantry 10 , which allows the locking ball 14 immediately from the seat 13 separates. This opens the channel 11 , which allows the hydraulic oil in the pantry 10 through the channel 11 in the pressure chamber 9 flows. The piston 2 and the push bar 4 Thus, they can move smoothly and smoothly outwards to immediately tighten the belt again.

While the machine is running, the belt vibrates at a high frequency such that the locking ball 14 the check valve 12 moved between its closed and the open positions at a high speed and to the seat 13 in short intervals abuts. The blocking ball 14 and the seat 13 therefore, tend to be worn out. Because the blocking ball 14 is rotatable, it touches the seat 13 not in a fixed position, but in different places. But, because the seat 13 the blocking ball 14 touched at a fixed point, the seat tends 13 in addition, stronger than the blocking ball 14 to be worn down.

To the wear resistance of particular the seat 13 To be able to increase, therefore, the blocking ball 14 made of a bearing steel and is hardened while the piston 2 is made of a chrome steel or a chromium molybdenum steel and the seat surface 13 with a wear-resistant film 16 is coated.

In the embodiment, the wear-resistant film is 16 a composite comprising a mixture of metallic chromium, dichromomononitrile (Cr ₂ N) and monochrome mononitride (CrN). But the movie 16 according to the invention may be a composite comprising a mixture of metallic chromium and monochrome mononitride (CrN).

The wear-resistant film 16 is preferably 1 to 10 microns thick.

The wear-resistant film 16 which mainly comprises a metallic chromium and a chromium nitride or chromium nitrides has excellent wear resistance, adhesiveness and hardness, and therefore improves the wear resistance of the seat surface 13 and extends the service life of the hydraulic tensioner. The film 16 also makes it possible to use the tensioner under high loads.

The seat is preferred 13 subjected to a lapping before the seat 13 with a wear-resistant film 16 is coated, or the wear-resistant film 16 is lapped after being coated to improve the surface smoothness of the film 16 improve the possibility of breaking the film 16 is minimized and its load resistance is improved.

It is also possible by removing the seat 13 of the piston 2 subjected to a hard shot peening before the seat surface 13 with the wear-resistant film 16 is coated, or by the surface of the wear-resistant film 16 subjected to hard shot peening after coating, the load resistance of the wear-resistant film 16 and also the piston 2 to improve and thus to be able to use the hydraulic tensioner under high loads.

Three samples (Nos. 1 to 3) according to the present ing invention have been made, of which the seat 13 with a wear-resistant film 16 coated with a thickness of 5 μm and made of a composite material comprising a mixture of metallic chromium, Cr ₂ N and CrN. They were based on abrasion or abrasion of the seat 13 tested. 3A shows the results. For comparison, three samples (Nos. 4 to 6) having no wear-resistant film and three samples (Nos. 7 to 9) having a 4 μm-thick wear-resistant titanium nitride (TiN) film resting on the seating surface 13 was formed, produced. These samples were for wear or abrasion of the seat 13 tested. The test results are in 3B and 3C shown.

The piston 2 Each of samples Nos. 1 to 9 was made of molybdenum steel. In the test, the ball was 14 repeatedly on the seat 13 of the piston 2 beaten.

The ball 14 was made of bearing steel or ball bearing steel and hardened.

The test conditions were as follows:
Frequency: 300 Hz
Input load: 1700 N
Temperature: 100 ° C
Number of cycles: 5 × 10 ⁶

How out 3 it can be seen is that the seats 13 The samples of the present invention (Nos. 1 to 3) are excellent in wear resistance.

In 1 a hydraulic tensioner is shown for regulating the belt tension. But the hydraulic tensioner according to the present invention is not limited thereto, but may be a chain tensioner, as in FIG 4 will be shown.

The chain tensioner in 4 is shown contains a housing 30 as a cylinder, a piston 32 sliding in a cylinder chamber 31 is housed in the housing 30 is formed, and a spring 33 in the cylinder chamber 31 is set up and the piston 32 outward from the cylinder chamber 31 biases. The housing 30 is with an oil supply duct 35 formed with a pressure chamber 34 connected in the cylinder chamber 31 behind the piston 32 is trained. At the oil outlet of the canal 35 is a check valve 36 provided to prevent hydraulic oil in the pressure chamber 34 in the channel 35 can flow back.

The check valve 36 contains a valve seat 37 in the cylinder chamber 31 is set up and with a channel 38 is formed, through which the Ölzuführkanal 35 with the pressure chamber 34 connected, a blocking ball 40 that are in contact with a seat 39 of the valve seat 37 can move and move out of contact with this, and a bracket 41 for restricting the movement of the blocking ball 40 and thus the degree of opening of the channel 38 ,

The piston 32 is with an axial bore 42 formed, which opens at its rear end and an internal thread 43 on its inner wall next to its rear opening. The screw rod 44 is in the axial bore 42 with its external thread 45 on its outer circumference in threaded engagement with the internal thread 43 used. The screw rod 44 is with an axial bore 46 trained, which opens at its front end. A feather 47 is in the axial bore 46 with its front end in abutment with the closed end of the axial bore 42 and with its rear end in abutment with the closed end of the axial bore 46 attached, causing the piston 32 and the screw rod 44 be biased in opposite directions.

Both the internal thread 43 as well as the external thread 45 have a pressure flank 48 on which the pushing force from the spring acts, and a clearance flank 49 which has a smaller flank angle than the pressure flank 48 , The threads 43 and 45 therefore have a rib-shaped cut. In addition, the rib-shaped threads have 43 and 45 a front angle, so the screw rod 44 is axially movable while moving under the force of the spring 47 rotates.

This chain tensioner is used for the piston 32 , which tends to stick outward, tends to push a camshaft drive chain (not shown) and, if the chain is loose, causes the spring 33 that the piston is 32 moved outward, whereby the game or the looseness of the chain is recorded.

At the movement of the piston 32 the wrench also moves outwards 44 together with the piston from the valve seat 37 path. When the piston 32 As the chain absorbs and stops, the tie rod retracts 44 back while he is under the power of the spring 47 turns until he touches the valve seat 37 strikes.

When the piston 32 moved outward, the pressure falls in the pressure chamber 34 off, causing the blocking ball 40 from the seat 39 is disconnected. Hydraulic oil thus flows into the pressure chamber 34 through the channel 35 ,

As the chain tension increases and a pushing force on the piston increases 32 is applied, the pressure in the pressure chamber increases 34 of the kind of that the blocking ball 40 to the seat 39 strikes and the channel 38 closes. The pressing force on the piston 32 is applied, is thus by the composite force from the pressure of the hydraulic oil in the pressure chamber 34 and the power of the spring 33 attenuated.

When the pressing force exceeds this composite force, hydraulic oil enters the pressure chamber 34 through a gap between the inner wall of the cylinder chamber 31 and the piston 32 out, which allows the piston 32 retracts while spinning until the oppressive force is in balance with the compound force.

With this chain tensioner it is also possible by the seat surface 39 with a wear-resistant film 16 of a composite material comprising a mixture of metallic chromium, dichromomononitrile (Cr ₂ N) and monochrome mononitride (CrN), or with a wear resistant film 16 is coated from a composite comprising a mixture of metallic chromium and CrN, the resistance to wear of the seat 39 is layered, the wear resistance of the seat 39 to improve.

In this case, it is possible by lapping or by hard shot peening, the load resistance of the wear-resistant film 16 to improve.

Claims (6)

A hydraulic tensioner comprising a cylinder filled with a hydraulic oil, a piston slidably disposed in the cylinder so as to divide the inside of the cylinder into a pressure chamber and a reservoir, a push rod so arranged in the cylinder in that it moves axially with the piston and has a free end which protrudes from the cylinder, a spring which is arranged in the cylinder and which biases the piston and the push rod outwards from the cylinder, the piston having a Channel defines, by which the pressure chamber is in communication with the storage chamber, and having a locking ball which is adapted to be held in contact with the valve seat surface which is formed on a surface of the channel, whereby the channel is closed when the Pressure in the pressure chamber is higher than the pressure in the reservoir chamber, and otherwise designed to be separated from the valve seat surface to be; characterized in that the valve seat surface is coated with a wear resistant film of a composite comprising a mixture of a metallic chromium, a dichromononitrile Cr ₂ N and a monochrome mononitride CrN. Hydraulic tensioner, a cylinder that with a hydraulic oil filled is a piston which is slidably arranged in the cylinder so is that he puts the inside of the cylinder into a pressure chamber and a Pantry divided, a push bar, in the cylinder is arranged so that it moves axially with the piston, and having a free end protruding from the cylinder, one Spring, which is mounted in the cylinder and the piston and the push bar to the outside biased by the cylinder, wherein the piston defines a channel, through which the pressure chamber is connected to the storage chamber, and a locking ball designed to be in contact with the valve seat surface to be held, which formed on a surface of the channel is, whereby the channel is closed when the pressure in the pressure chamber higher than the pressure in the pantry is, and otherwise designed is, from the valve seat surface to be separated; characterized in that the valve seat surface with a wear resistant film is coated from a composite, the a mixture of metallic chromium and monochrome mononitride CrN having. A hydraulic tensioner comprising a housing bounding a cylinder chamber, a piston slidably disposed in the cylinder chamber defining a pressure chamber behind the piston, a spring disposed in the cylinder chamber, and the piston outwardly from the cylinder chamber biased, the housing defining an oil supply passage having an oil outlet communicating with the pressure chamber and having a locking ball adapted to be held in contact with the valve seat surface formed on a surface of the oil outlet; whereby the oil supply passage is closed when the pressure in the pressure chamber is higher than the pressure in the oil supply passage, and is otherwise adapted to be separated from the valve seat surface; characterized in that the valve seat surface is coated with a wear resistant film of a composite comprising a mixture of metallic chromium, dichromomononitrile Cr ₂ N and monochrome mononitride CrN. A hydraulic tensioner comprising a housing defining a cylinder chamber, a piston slidably mounted in the cylinder chamber so as to define a pressure chamber behind the piston, a spring disposed in the cylinder chamber, and the piston outwardly from the cylinder chamber, the housing defining an oil supply passage having an oil outlet communicating with the pressure chamber and having a locking ball adapted to be held in contact with the valve seat surface located on the surface of the oil outlet is formed, whereby the oil supply channel is closed when the pressure in the pressure chamber is higher than the pressure in the oil supply passage, and is otherwise adapted to be separated from the valve seat surface; characterized in that the valve seat surface is coated with a wear resistant film of a composite material comprising a mixture of metallic chromium and monochrome mononitride CrN. Hydraulic tensioner according to one of claims 1 to 4, wherein the valve seat surface a lapping before it is coated with the wear-resistant film will, or the surface the wear-resistant film is lapped after the valve seat surface has been coated with the wear-resistant film. Hydraulic tensioner according to one of claims 1 to 5, wherein the entire valve seat surface subjected to shot peening before being coated with the wear-resistant film, or in which the surface of the wear-resistant film is subjected to shot peening after the valve seat surface has been coated with the wear-resistant film.