JPH064407U - Fluid pressure cylinder - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the weight of the entire cylinder without reducing the fatigue life. [Structure] The thickness t3 of the portion 11b of the cylinder tube 11 excluding the end 11a on the head cover side is
By forming the head cover side end portion 11a smaller than the wall thickness dimension t2 and providing the reinforcing layer 15 made of fiber reinforced plastic on the outer periphery of the portion 11b having the smaller wall thickness dimension, the fatigue life is as long as the conventional one. While trying to reduce the weight.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lightweight fluid pressure cylinder (hydraulic cylinder, pneumatic cylinder, etc.).

[0002]

[Prior art]

 The fluid pressure cylinder is usually made of metal such as steel, and as shown in FIG. 4, a head cover 2 is joined to one end of a cylinder tube 1 and a rod cover 3 is joined to the other end by back welding. W1 and W2 are welded portions of the cylinder tube 1 and both side covers 2 and 3.

In this case, the backing metal on the side of the rod cover 3 is removed by cutting after welding, but the backing metal 4 on the side of the head cover 2 cannot be removed and is left as it is. As a result, the unwelded portion S remains in a crack between the backing plate 4 and the inner surface of the tube.

By the way, the wall thickness dimension t0 of the cylinder tube 1 is calculated as a value at which the stress generated in the cylinder tube 1 is equal to or lower than the design allowable stress based on the maximum working pressure of the cylinder and the safety factor.

In this case, when the internal pressure acts on the cylinder, the stress generated in the cylinder circumferential direction becomes considerably larger than that in the cylinder axial direction. Therefore, the wall thickness dimension t0 is determined on the basis of the stress in the cylinder circumferential direction. To be

Therefore, considering the stress in the cylinder axial direction as a reference, the wall thickness of the cylinder tube 1 is unnecessarily increased, and as a result, the cylinder becomes heavier and the construction machine such as a hydraulic excavator is eventually used. When it is used in a machine in which dynamic characteristics are a problem, the dynamic characteristics are supposed to deteriorate due to its weight.

Conversely, if the weight of the cylinder can be reduced, the dynamic characteristics of such a construction machine can be improved.

As a means for reducing the weight of this cylinder, it is conceivable to use a fiber reinforced plastic such as a carbon fiber reinforced plastic as a constituent material, as employed in the field of pressure vessels and the like.

In this case, as a basic method, as shown in FIG. 5, the wall thickness dimension t1 of the cylinder peripheral wall (the cylinder tube 1 and the joints of the both side covers 2 and 3 to the tube 1) is determined by the conventional method. The reinforcing layer 5 is wound in the cylinder circumferential direction by a filament wind method or the like by winding a fiber-reinforced plastic, that is, a bundle of resin-impregnated reinforcing fibers on the outer periphery of which is smaller than the wall thickness dimension t0 (for example, about 1/2). A method of forming is conceivable.

According to such a cylinder configuration, the load in the cylinder axial direction is received by the cylinder tube (metal portion) 1, and the load in the cylinder circumferential direction is shared by the cylinder tube 1 and the reinforcing layer 5. By doing this, it is possible to reduce the weight of the cylinder while ensuring the required cylinder strength.

[0011]

[Problems to be solved by the device]

 However, in this way, since the thickness of the cylinder tube 1 is reduced, the degree of concentration of stress on the unwelded portion S of the welded portion W1 of the tube 1 and the head cover 2 during use is shown in FIG. Since the size of the crack is larger than that of the manufactured one, the crack in the unwelded portion S 3 easily propagates from the tip side to the center side, and the number of pressure repetitions until the crack reaches the outer periphery of the welded portion 4 decreases.

That is, with the configuration shown in FIG. 5, weight reduction can be achieved, but there is an adverse effect that the fatigue life is significantly reduced.

Therefore, the present invention provides a fluid pressure cylinder capable of achieving weight reduction without causing such a decrease in fatigue life.

[0014]

[Means for Solving the Problems]

 According to a first aspect of the present invention, in a fluid pressure cylinder in which a head cover is joined to one end of a cylinder tube and a rod cover is joined to the other end by welding, the wall thickness of the cylinder tube is such that the end portion on the head cover side is the same. A portion excluding the head cover is formed smaller than the end portion on the side of the head cover, and a reinforcing layer made of fiber reinforced plastic is provided on the outer periphery of the portion having a small wall thickness.

According to a second aspect of the present invention, in a fluid pressure cylinder configured by welding a head cover to one end of a cylinder tube and a rod cover to the other end by welding, the thickness of a portion of the cylinder tube excluding both ends thereof. The dimension is smaller than the wall thickness at both ends, and a reinforcing layer made of fiber reinforced plastic is provided on the outer periphery of the portion having the smaller wall thickness.

[0016]

[Action]

 According to the configuration of claim 1, in comparison with the conventional cylinder, the wall thickness of the end portion of the cylinder tube on the head cover side is the same as that of the conventional cylinder, and the wall thickness of the remaining portion that occupies most of the cylinder tube. By making the size smaller than before, it is possible to secure the same fatigue life of the welded portion between the tube and the head cover as before (without reducing the fatigue life), while achieving weight reduction.

According to the second aspect of the present invention, since the wall thickness of the end portion of the cylinder tube on the side of the head cover and the end portion on the side of the rod cover are increased, the welded portion between the tube and the rod cover is increased. There is no fear of shortening the fatigue life.

[0018]

【Example】

 First Embodiment (see FIGS. 1 and 2) 11 is a cylinder tube, 12 is a head cover, and 13 is a rod cover, which are made of metal such as steel as in the past and are joined by backing welding. W3 and W4 are welded portions on both sides, and 14 is a backing metal provided on the inner periphery of the welded portion W3 of the cylinder tube 11 and the head cover 12.

The cylinder tube 11 has a difference in thickness t2, t3 between the end 11a on the side of the head cover 12 and the other portion (a portion that occupies most of the entire tube length, hereinafter referred to as the main body portion) 11b. Have That is, the thickness t2 of the head-side end portion 11a is relatively large and the thickness t3 of the main body portion 11b is relatively small.

The thickness of the portions of the both side covers 12 and 13 to be welded to the cylinder tube 11 are also different according to the thicknesses t 2 and t 3 of the portions 11 a and 11 b of the cylinder tube 11. ing.

The cylinder tube 11 is provided with a reinforcing layer 15 made of fiber reinforced plastic such as carbon fiber reinforced plastic on the outer periphery of the main body portion 11b, and a load in the cylinder circumferential direction is applied to the cylinder tube 11 and the reinforcing layer 15. It is configured to be shared by and.

The reinforcing layer 15 is formed by winding a bundle of reinforcing fibers impregnated with resin in the cylinder circumferential direction, as described in the section of the related art.

In this configuration, in comparison with the conventional metal-made cylinder shown in FIG. 4, by setting t0 = t2 under the condition that the total cylinder length and the inner diameters of the cylinder tubes 1 and 11 are the same, The fatigue life of the welded portion W3 between the cylinder tube 11 and the head cover 12 can be secured to the same extent as the fatigue life of the welded portion W1 in the conventional cylinder, and further, the weight of the entire cylinder is reduced because of the relationship of t1 (t2)> t3. You can

Second Embodiment (see FIG. 3) In the welded portion W4 between the cylinder tube 11 and the rod cover 13, unlike the welded portion W3 on the opposite side, the backing metal is removed after welding, and therefore the unwelded portion is Since it does not occur, theoretically, the fatigue life does not decrease even if the wall thickness is reduced as in the first embodiment.

However, in reality, there is a high possibility that the stress concentration will occur more than in the non-welded portion due to other factors such as incomplete welding, and the fatigue life may be reduced when the wall thickness dimension is reduced. is there.

Therefore, in the second embodiment, in consideration of safety in such a case, the wall thickness dimension t4 of the rod cover side end portion 11c of the cylinder tube 11 is set to the head cover side end portion thickness t2. In the same manner, the thickness t3 of the remaining portion 11d is made smaller than these thicknesses t2 and t4 at both ends, and the reinforcing layer 15 is provided on the outer periphery thereof.

In order to confirm the effect of the present invention, the present inventor has confirmed that the conventional metal cylinder (referred to as cylinder A) shown in FIG. 4 and the cylinder (cylinder B) shown in FIG. 1), a cylinder according to the first embodiment of the present invention shown in FIG. 1 (referred to as cylinder C), and a cylinder according to the second embodiment of the present invention shown in FIG. Got the result.

Each of the cylinders A, B, C, and D was made of steel, and had a total length of 1200 mm and a cylinder tube inner diameter of 95 mm. Carbon fiber reinforced plastic was used for the reinforcing layers 5 and 15 of the cylinders B, C and D.

[0029]

[Table 1]

As shown in the above table, in comparison to cylinder A, cylinder C has a weight of 5.8 kg and cylinder D has a weight of 5. A weight reduction of 6 kg was achieved.

When the cylinder is made lighter, when it is used in a construction machine such as a hydraulic excavator, the working part is made lighter to improve the dynamic characteristics, and the counterweight for balancing with the working part is made lighter. Various effects such as improved characteristics and improved fuel efficiency due to overall weight reduction can be obtained.

Further, the present inventor conducted a fatigue test on each of the cylinders B, C and D. The test is a 2P pulse endurance test (leakage at 150,000 times, if there is no damage, it is passed) by repeatedly applying a pulse pressure twice the maximum operating pressure to the cylinder and checking the occurrence of cylinder leakage and damage. went.

As a result, the cylinder B failed the test after leaking from the welded portion after the pressure was repeated 130,000 times, while the cylinders C and D were leaked after the pressure was repeated 150,000 times. It was qualified for the 2P pulse test as having no fatigue and having sufficient fatigue life.

[0034]

[Effect of device]

 As described above, according to the first aspect of the invention, the thickness of the portion of the cylinder tube excluding the end on the head cover side is made smaller than the thickness of the end on the head cover side. Since a reinforcement layer made of fiber reinforced plastic was provided on the outer periphery of the small part of the cylinder, the wall thickness of the end of the cylinder tube on the head cover side was the same as that of the conventional cylinder, and most of the cylinder tube was By reducing the wall thickness of the remaining part that occupies the area compared to the conventional method, it is possible to realize the weight reduction while ensuring the same fatigue life of the welded part of the tube and the head cover as before. .

Therefore, when used in a machine such as a construction machine such as a hydraulic excavator in which dynamic characteristics are a problem, it is possible to improve the dynamic characteristics of the machine and improve fuel efficiency.

Further, according to the second aspect of the invention, since the wall thickness of the head side end of the cylinder tube and the rod cover side end of the cylinder tube are increased, fatigue at the welded portion between the tube and the rod cover is increased. There is no risk of shortening the life.

[Brief description of drawings]

FIG. 1 is a half sectional front view showing a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a front view of a half section showing a second embodiment of the present invention.

FIG. 4 is a front view showing a half section and a partially enlarged view of a conventional all-metal cylinder.

FIG. 5 is a front view of a half section of a cylinder in which the wall thickness of the cylinder tube is thinned and a reinforcing layer made of fiber reinforced plastic is provided on the outer periphery as a means for weight reduction.

[Explanation of symbols]

11 Cylinder tube 11a Head cover side end of cylinder tube 11b Portion other than head cover side end of the same tube 11c Rod cover side end of the same tube 11d Portion other than both ends of the same tube 12 Head cover 13 Rod cover 15 From fiber reinforced plastic Reinforcement layer

Claims (2)

[Scope of utility model registration request] 1. In a fluid pressure cylinder configured by welding a head cover to one end of a cylinder tube and a rod cover to the other end, the thickness of a portion of the cylinder tube excluding the end on the head cover side. The fluid pressure cylinder is characterized in that it is formed to be smaller than the wall thickness dimension of the end portion on the head cover side, and a reinforcing layer made of fiber reinforced plastic is provided on the outer periphery of the portion having the smaller wall thickness dimension. 2. A fluid pressure cylinder comprising a head cover and a rod cover, which are joined to one end of a cylinder tube by welding and the other end of the cylinder tube, respectively. A fluid pressure cylinder characterized in that it is formed to be smaller than the wall thickness dimension, and a reinforcing layer made of fiber reinforced plastic is provided on the outer periphery of the portion having the smaller wall thickness dimension.