Bearing for supporting swash plate of hydrostatic continuously variable transmission

Abstract

The present invention relates to a bearing for supporting an inclined plate of a hydrostatic continuously variable transmission. According to the present invention, a technique is disclosed in which a plate material of an aluminum material and a Teflon material are joined, or a separate fixing portion that does not contact the support portion is formed and fixed to the support portion, so that control for neutral return is easy, and manufacturability and versatility are improved.

Description

Technical Field

[0001] The present invention relates to a bearing for supporting a swash plate provided in a hydrostatic continuously variable transmission.

Background Art

[0002] A hydrostatic continuously variable transmission is mounted on a work vehicle that frequently shifts gears due to the operating characteristics. In particular, the hydrostatic continuously variable transmission is appropriately applied to agricultural work vehicles (such as agricultural tractors, combines, and rice transplanters).

[0003] The hydrostatic continuously variable transmission is continuously variable and is composed of a hydraulic motor, a hydraulic pump, etc.

[0004] The hydraulic motor generates a rotational force on the output shaft by hydraulic pressure due to the flow rate of the working fluid coming from the hydraulic pump.

[0005] The hydraulic pump operates by the rotational force output from the engine, sucks in the flow rate, and provides it to the hydraulic motor. That is, the hydraulic pump provides hydraulic pressure to the hydraulic motor, and the hydraulic motor operates by the hydraulic pressure coming from the hydraulic pump.

[0006] The hydraulic pump is provided with a swash plate for shifting gears, and the gear is shifted by changing the angular position of the swash plate due to rotation. Also, forward or reverse shifting can be performed depending on the rotational direction of the swash plate in the neutral position. For example, FIG. 1 shows the angular positions of various swash plates SP in relation to the support portion (or also referred to as "guide") SB. (a) of FIG. 1 shows the forward state, (b) of FIG. 1 shows the neutral (stationary) state, and (c) of FIG. 1 shows the reverse state.

[0007] The hydrostatic continuously variable transmission performs continuously variable speed increase and decrease by changing the flow rate provided to the hydraulic motor according to the angular position of the swash plate SP. That is, the hydraulic pump is configured as a variable displacement type that executes shifting by varying the flow rate provided to the hydraulic motor. And the degree of variable displacement is determined by the angular position (rotational direction and amount of rotation) of the swash plate SP.

[0008] In recent years, in order to vary the torque of the output shaft, a swash plate SP may be applied to a hydraulic motor in some cases.

[0009] During rotation for changing the angular position of the swash plate SP, a great deal of friction and heat are generated. Therefore, a metal bearing is mounted on the support portion SB for smooth rotation of the swash plate SP. That is, the swash plate SP does not directly contact the support portion SB, and a bearing is interposed between the swash plate SP and the support portion SB.

[0010] Generally, the angular position conversion of the swash plate SP is performed by the operation of the driver.

[0011] Therefore, without the operation of the driver, the angular position of the swash plate SP must return to the neutral return angle. Here, the neutral return angle refers to the angular position of the swash plate SP within the range where the output shaft of the hydrostatic continuously variable transmission can stop by itself. For example, when the swash plate SP returns within the neutral return angle, theoretically, the angular position of the swash plate SP can return to 0 degrees of the neutral position due to the slip between the swash plate SP and the bearing.

[0012] By the way, the frictional resistance between the swash plate SP and the bearing acts as an obstructive element to returning the angular position of the swash plate SP to the neutral position. That is, if the frictional resistance between the swash plate SP and the bearing is large, it may be difficult for the swash plate SP to return to the neutral position.

[0013] The frictional resistance can vary depending on the shape and material of the bearing.

[0014] On the other hand, the operation of the driver can be input to the swash plate SP electronically or mechanically. In either case, a mechanical structure for inputting a rotational force to the swash plate SP is required.

[0015] The tolerances of the mechanical structure must be controlled to such an extent that the swash plate SP can be returned within the neutral return angle.

[0016] If the neutral return angle is large, the tolerances of the mechanical structure can be managed slightly wider.

[0017] On the other hand, if the neutral return angle is small, the tolerances of the mechanical structure must be managed precisely. Also, there may be a defect in the neutral return of the swash plate SP even slightly. And all of these points are accompanied by an increase in production cost.

[0018] On the other hand, depending on the specifications of the bearing, the neutral return angle may be small or may be large.

[0019] If a high-performance bearing is applied, the neutral return angle can be increased by its performance. And if the neutral return angle is large, tolerance management becomes easy, production cost can be reduced, and the reliability of the equipment can be improved.

[0020] Since the present invention relates to a bearing, the conventional bearing will be further described below.

[0021] As shown in FIG. 2, the conventional bearing 200 is composed of a first plate 210 made of a synthetic resin material and a second plate 220 made of a metal material.

[0022] The first plate 210 is made of a polytetrafluoroethylene (so-called "Teflon (registered trademark)") material.

[0023] The second plate 220 is made of a steel material.

[0024] A fixing hole FH is formed in the central region of the bearing 200, and positioning holes PH are formed on both sides of the fixing hole FH.

[0025] FIG. 3 shows the coupling relationship between the support part SB to which the bearing 200 of FIG. 2 is attached and the bearing 200.

[0026] In the central region of the support part SB, fixing screw holes FG are formed at positions corresponding to the fixing holes FH. And on both sides of the fixing screw holes FG, positioning protrusions PP are formed at positions corresponding to the positioning holes PH.

[0027] The fixing screw FS fixes the bearing 200 to the support part SB through the fixing hole FH and the fixing screw hole FG.

[0028] The fixing screw FS needs to be tightened firmly to closely adhere the bearing 200 and the support part SB. That is, there should be no space between the bearing 200 and the support part SB. By doing so, the swash plate SP can be properly assembled.

[0029] Generally, the swash plate SP rotates in a state of closely adhering to the bearing 200. Therefore, if the slippage between the swash plate SP and the bearing 200 is not appropriate, the surface (contact surface) of the first plate 210 will be pushed by the frictional resistance. That is, a phenomenon occurs in which the surface of the polytetrafluoroethylene material is wound while being pushed by the frictional resistance. Such a phenomenon is prevented by the positioning protrusions PP arranged on both sides of the fixing screw FS to determine the position of the bearing 200.

[0030] However, the conventional bearing 200 has the following problems.

[0031] First, due to the thickness of the second plate 220 made of steel material, the manufacturability of the bearing 200 is not good.

[0032] The fixing screw FS and the swash plate SP must not interfere with each other. Therefore, the head of the fixing screw FS needs to be deeply pushed in so as not to protrude from the surface of the bearing 200. For this purpose, the second plate 220 must ensure its depth. For this reason, the thickness of the second plate 220 increases, and the rigidity increases accordingly, so there is difficulty in manufacturing the shape of the second plate 220.

[0033] Second, the assemblability deteriorates due to the shape restoring force.

[0034] Even when the shape of the second plate 220 is fabricated, the shape of the second plate 220 may be restored by its own elastic restoring force. In that case, the operation of fixing the bearing 200 to the support portion SB becomes complicated.

[0035] Third, the productivity of the bearing 200 decreases.

[0036] A total of three holes FH and PH are formed in the bearing 200. The surface roughness of the bearing 200 deteriorates due to burrs or the like generated when forming the holes FH and PH. Then, scratches or the like occur on the inclined plate SP, increasing the frictional resistance. Therefore, the surface of the bearing 200 after the hole forming operation must be finished smoothly. Furthermore, the productivity decreases accordingly.

[0037] Fourth, it may not be possible to ensure the standardization of each product.

[0038] For example, the standards of the holes FH and PH may not exactly match for each product. In this case, the surface friction coefficient may vary for each product. Then, the reliability of the product decreases due to the non-uniformity in which the characteristics change for each finished product (inclined plate assembly).

[0039] Fifth, there is the trouble that a separate positioning projection PP must be formed on the support portion SB.

[0040] Sixth, since it is difficult to manage the friction coefficient and it is necessary to reduce the neutral return angle, it is necessary to precisely control the tolerance management and control design of the related mechanical structure. And such points ultimately increase the production cost.

Summary of the Invention

Problems to be Solved by the Invention

[0041] The present invention was devised to provide a technology that can solve the above-described problems.

Means for Solving the Problems

[0042] The swash plate support bearing according to the first aspect of the present invention is coupled to a support portion that supports a swash plate applied to a hydrostatic continuously variable transmission, and is provided between the swash plate and the support portion to reduce friction generated during rotation of the swash plate. The swash plate support bearing has a contact surface on one side that contacts the swash plate curved surface of the swash plate, and includes a first plate made of a synthetic resin material and a second plate made of a metal material that has a round and curved shape with curvature and is in close contact with and overlaps the other side of the first plate to maintain the shape of the first plate. The first plate is made of a polytetrafluoroethylene material.

[0043] It can be considered preferable that the second plate is made of an aluminum material.

[0044] The thickness of the first plate is 0.36 mm.

[0045] The friction coefficient of the contact surface is controlled to be 0.003 to 0.005.

[0046] The friction coefficient of the contact surface has a value such that the neutral return angle of the swash plate is 0.8 degrees to 1.5 degrees.

[0047] The first plate includes an internal core located between the one surface and the other surface, and the internal core is made of a metal material.

[0048] The internal core can be arranged in a mesh shape.

[0049] The first plate includes a contact portion having the contact surface, and a first fixing portion that bends and extends at both ends of the contact portion with the contact portion interposed therebetween and is fixed to the support portion. The second plate includes a coupling portion coupled to the contact portion, and a second fixing portion that bends and extends at both ends of the coupling portion with the coupling portion interposed therebetween and is fixed to the support portion together with the first fixing portion. The first fixing portion and the second fixing portion do not contact the swash plate.

[0050] The swash plate support bearing according to the second embodiment of the present invention is coupled to a support portion that supports a swash plate applied to a hydrostatic continuously variable transmission, and is provided between the swash plate and the support portion to reduce friction generated during rotation of the swash plate. The swash plate support bearing includes a first plate made of a synthetic resin material having a contact surface whose one surface contacts the swash plate curved surface of the swash plate, and a second plate made of a metal material having a shape that is rounded with curvature and that is in close contact with and overlaps the other surface of the first plate to maintain the shape of the first plate. The first plate includes an internal core located between the one surface and the other surface.

Advantages of the Invention

[0051] According to the present invention, the following effects are achieved.

[0052] First, by applying the second plate made of an aluminum material while being thinner than conventional ones, the manufacturability of the bearing is good.

[0053] Second, since the shape retention of the second plate is good, the assemblability is improved.

[0054] Third, since the fixing means is removed from the region where there is a contact surface that contacts the swash plate, the productivity of the bearing is improved.

[0055] Fourth, since at least the uniformity of the contact surface is ensured, the reliability of the product is improved.

[0056] Fifth, not only is there no need to separately form positioning protrusions on the support portion, but since long holes are applied, the versatility of the bearing is improved.

[0057] Sixth, since an appropriately large neutral return angle can be obtained as desired, production costs can be reduced.

Brief Description of the Drawings

[0058]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0059] Preferred embodiments according to the present invention will be described based on the accompanying drawings, but descriptions of well-known configurations will be omitted or reduced as much as possible for the sake of brevity of the description.

[0060] FIG. 4 is a schematic perspective view of a swash plate support bearing 100 (hereinafter abbreviated as "bearing") for a hydrostatic continuously variable transmission according to an embodiment of the present invention, and FIG. 5 is a schematic exploded view of the bearing 10 of FIG. 4.

[0061] Referring to FIGS. 4 and 5, the bearing 100 according to the present embodiment includes a first plate 110 and a second plate 120.

[0062] The first plate 110 is made of a synthetic resin material. More specifically, the first plate 110 is made of a polytetrafluoroethylene material.

[0063] The first plate 110 includes a contact portion 111 and first fixing portions 112a and 112b.

[0064] One surface of the contact portion 111 has a contact surface CF that contacts the swash plate SP.

[0065] The contact surface CF contacts an inclined plate surface having an arcuate and rounded curved surface. Therefore, the contact portion 111 is fabricated in a rounded and curved shape so as to have a curvature corresponding to the shape of the inclined plate surface.

[0066] The first fixing portions 112a and 112b are fixed to the support portion SB.

[0067] The first fixing portions 112a and 112b extend from both ends of the contact portion 111.

[0068] The first fixing portions 112a and 112b on both sides bend and extend from both ends of the contact portion 111 with the contact portion 111 interposed therebetween. The bending direction is a direction away from the inclined plate SP. Therefore, the first fixing portions 112a and 112b do not contact the inclined plate SP.

[0069] The second plate 120 is made of a metal material. According to a preferred exemplary embodiment of the present invention, the second plate 120 is made of an aluminum material. The aluminum material has good workability and shape retention. The second plate 120 functions to reinforce the rigidity and maintain the shape of the first plate 110.

[0070] The second plate 120 includes a coupling portion 121 and second fixing portions 122a and 122b.

[0071] The coupling portion 121 is coupled to the other surface of the contact portion 111. Therefore, the coupling portion 121 is fabricated in a rounded and curved shape so as to have a curvature corresponding to the shape of the contact portion 111. That is, according to the present embodiment, one surface of the first plate 110 has a contact surface CF that contacts the inclined plate surface, and the other surface of the first plate 110 is in close contact with and overlaps the second plate 120.

[0072] The second fixing portions 122a and 122b are coupled to the first fixing portions 112a and 112b. Further, the second fixing portions 122a and 122b are fixed to the support portion SB in a state of being coupled to the first fixing portions 112a and 112b.

[0073] The second fixing portions 122a and 122b extend from both ends of the coupling portion 121.

[0074] The second fixing parts 122a and 122b on both sides extend by bending from both ends of the connecting part 121 with the connecting part 121 interposed therebetween. The bending direction is the direction away from the inclined plate SP.

[0075] Therefore, the first fixing parts 112a and 112b and the second fixing parts 122a and 122b do not contact the inclined plate SP. This means that there is no need to consider the frictional resistance between the first fixing parts 112a and 112b and the inclined plate SP.

[0076] The first plate 110 and the second plate 120 have the same form and are overlapped and joined to each other.

[0077] On the other hand, referring to the cross-sectional photograph of FIG. 6, the first plate 110 has a thickness of approximately 0.36 mm, and the second plate 120 has a thickness of approximately 0.92 mm.

[0078] As confirmed by many experiments, the greater the thickness of the first plate 110, the gradually greater the friction coefficient of the contact surface CF. Conventionally, the friction coefficient of the contact surface CF was controlled in the range of 0.010 to 0.020. However, when the thickness of the first plate 110 is 0.36 mm as in this embodiment, the friction coefficient of the contact surface CF becomes as small as 0.003. However, if the thickness of the first plate 110 is smaller than 0.36 mm, it has been observed that the durability of the bearing 100 decreases.

[0079] The friction coefficient of the contact surface CF is related to the neutral return angle.

[0080] If the friction coefficient of the contact surface CF is 0.010 or more as in the conventional case, the neutral return angle becomes 0.3 degrees to 0.5 degrees. On the other hand, if the friction coefficient of the contact surface CF is 0.003 as in this embodiment, the neutral return angle becomes 0.8 degrees or more. This means that in the case of this embodiment, the design for returning the inclined plate SP to the neutral position becomes simple. According to the experiment of the embodiment to which the present invention is applied, it has been confirmed that even when the friction coefficient of the contact surface CF becomes 0.005, the neutral return angle can be maintained larger than 0.8 degrees.

[0081] Of course, if the neutral return angle is too large, the neutral starting angle will also increase. Here, the neutral starting angle refers to the angular position of the swash plate SP at which the output shaft reacts and rotates when the swash plate SP in the neutral position rotates.

[0082] For example, if the neutral starting angle is large, the reaction of the output shaft to the driver's operation will be delayed. In particular, in most cases, the neutral starting angle is larger than the neutral return angle. Therefore, it is necessary to consider that even if the neutral return angle is too large, the neutral starting angle will proportionally increase. Therefore, in the present invention, the friction coefficient of the contact surface CF is controlled to be 0.003 to 0.005, and the neutral return angle is controlled to be 0.8 degrees to 1.5 degrees.

[0083] According to this embodiment, the thickness of the second plate 120 is 0.92 mm. This is about half the thickness of the conventional one. The reason why the thickness can be reduced in this way is that the bearing 100 has separate fixing portions 112a, 112b / 122a, 122b in the region where it does not contact the swash plate SP. That is, since the bearing 100 is coupled to the support portion SB by separate fixing portions 112a, 112b / 122a, 122b that have nothing to do with the contact with the swash plate SP, the thickness of the second plate 120 can be significantly reduced.

[0084] In this way, since the thickness of the second plate 120 can be reduced, the formability of the bearing 100 is further improved. And since it is made of an aluminum material, it is not only lighter but also has good shape retention and the assemblability of assembling the bearing 100 to the support portion SB is also improved.

[0085] Also, referring to FIG. 6, it can be confirmed that the internal core IW is arranged in the first plate 110.

[0086] The inner core IW is for preventing the phenomenon that the first plate 110 is pushed and wound due to the friction with the swash plate SP. For this purpose, the inner core IW needs to be made of a material with higher rigidity than the first plate 110. More specifically, in this embodiment, the inner core IW is made of a metal material. In particular, the inner core IW can be made of a rigid steel material. The inner core IW serves to support the first plate 110 so that it is not pushed even when frictional resistance occurs between the rotating swash plate SP and the contact surface CF.

[0087] In this way, since the inner core IW supports the first plate 110 so that it is not wound, according to the present invention, separate positioning holes PH and positioning protrusions PP are not necessary.

[0088] The inner core IW can be designed to be arranged in a mesh shape. The mesh arrangement enables the inner core IW to maintain the form of the first plate 110 against frictional forces applied in various directions. On the other hand, fixing holes FH are formed in the first fixing portions 112a, 112b and the second fixing portions 122a, 122b.

[0089] The bearing 100 according to the present invention is used in a structure for supporting the swash plate SP of a hydrostatic continuously variable transmission.

[0090] A hydrostatic continuously variable transmission is provided with a hydraulic pump and a hydraulic motor in pairs. The swash plate SP is provided in the hydraulic pump, and may also be provided in the hydraulic motor at this time.

[0091] As shown in the reference diagram of FIG. 7, generally, the swash plate SP is installed to be supported by the support portion SB.

[0092] By the way, since the swash plate SP rotates, friction may occur between the rotating swash plate SP and the support portion SB when the swash plate SP rotates. Therefore, in order to reduce friction, it is necessary to interpose the bearing 100 between the swash plate SP and the support portion SB.

[0093] According to this embodiment, a fixing screw hole FG is formed in the support portion SB at a position corresponding to the fixing hole FH. Therefore, the bearing 100 can be fixedly installed on the support portion SB by the fixing screw FS. For this purpose, the contact portion 111 and the coupling portion 121 do not have to be provided with fixing means for fixing to the support portion SB.

[0094] The fixing screw FS fixes the bearing 100 to the support portion SB in both side regions outside the contact surface CF. Therefore, the fixing screw FS also functions to prevent the phenomenon of the contact surface CF being pushed in the entire region of the contact surface CF where friction with the inclined plate SP occurs. Of course, as described above, the internal core IW also prevents the phenomenon of the contact surface CF being pushed, but the fixing screw FS further reinforces the function of preventing the push.

[0095] In addition, the fixing hole FH has a form of a long hole that is long in a direction approximately perpendicular to the line segment connecting both fixing holes FH. The long-hole-shaped fixing hole FH enables the bearing 100 to be appropriately and fixedly installed on the support portion SB even if the specifications of the support portion SB are slightly different. In this way, the versatility of the bearing 100 is improved by forming the long-hole-shaped fixing hole FH and not providing a separate positioning projection PP on the support portion SB.

[0096] On the other hand, the present invention generally has the characteristics of forming the second plate 120 from an aluminum material and reducing the thickness, coupling the bearing 100 to the support portion SB at both end portions of the bearing 100 that do not contact the inclined plate SP, and providing the internal core IW in the first plate 110. And these three major characteristics can be individually or selectively applied to the bearing 100, or can be applied to the bearing 100 together as in the above-described embodiment.

[0097] The above-described embodiments are merely examples for explaining the preferred examples of the present invention, and can have various application forms. Therefore, the present invention should not be understood only within the scope of the above-described content. Instead, the scope of rights of the present invention should be understood by the scope of the claims described separately and its equivalent scope.

Claims

1. It is coupled to a support portion (SB) that supports an inclined plate (SP) applied to a hydrostatic continuously variable transmission, and is provided between the inclined plate (SP) and the support portion (SB) to reduce friction generated during rotation of the inclined plate (SP). An inclined plate support bearing (100), comprising: A first plate (110) made of a synthetic resin material having a contact surface (CF) on one surface of which contacts the inclined surface of the inclined plate (SP); A second plate (120) made of a metal material having a shape that is rounded with a curvature and is in close contact with and overlaps the other surface of the first plate (110) to maintain the shape of the first plate (110), and The first plate (110) is made of polytetrafluoroethylene material, and is an inclined plate support bearing for a hydrostatic continuously variable transmission.

2. The second plate (120) is made of aluminum material, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 1.

3. The thickness of the first plate (110) is 0.36 mm, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 1.

4. The friction coefficient of the contact surface (CF) is 0.003 to 0.005, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 1.

5. The friction coefficient of the contact surface (CF) has a value such that the neutral return angle of the inclined plate is 0.8 degrees to 1.5 degrees, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 4.

6. The first plate (110) includes an internal core (IW) located between the one surface and the other surface, The internal core (IW) is made of a metal material, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 1.

7. The internal core (IW) is arranged in a mesh (mesh) shape, and is the inclined plate support bearing for a hydrostatic continuously variable transmission according to Claim 6.

8. The first plate (110) is a contact portion (111) having the contact surface (CF), and first fixing portions (112a, 112b) that are bent and extend at both ends of the contact portion (111) with the contact portion (111) interposed therebetween and are fixed to the support portion (SB), The second plate (120) is a coupling portion (121) coupled to the contact portion (111), and second fixing portions (122a, 122b) that are bent and extend at both ends of the coupling portion (121) with the coupling portion (121) interposed therebetween and are fixed to the support portion (SB) together with the first fixing portions (112a, 112b), The first fixing portions (112a, 112b) and the second fixing portions (122a, 122b) do not contact the inclined plate (SP). The bearing for supporting the inclined plate of the hydrostatic continuously variable transmission according to claim 1.

9. Fixing holes (FH) are formed in the first fixing portions (112a, 112b) and the second fixing portions (122a, 122b). The bearing for supporting the inclined plate of the hydrostatic continuously variable transmission according to claim 8.

10. The fixing hole (FH) is an elongated hole. The bearing for supporting the inclined plate of the hydrostatic continuously variable transmission according to claim 9.

11. The contact portion (111) and the coupling portion (121) do not include fixing means for being fixed to the support portion (SB). The bearing for supporting the inclined plate of the hydrostatic continuously variable transmission according to claim 8.

12. A bearing (100) for supporting an inclined plate (SP) that is coupled to a support portion (SB) for supporting the inclined plate (SP) applied to a hydrostatic continuously variable transmission, and is provided between the inclined plate (S) and the support portion (SB) to reduce friction generated during rotation of the inclined plate (S), including a contact surface (CF) one surface of which contacts the inclined surface of the inclined plate (SP), and a first plate (110) made of a synthetic resin material, It has a shape that is rounded and curved to have curvature, and includes a second plate (120) made of a metal material that is in close contact with and overlaps the other surface of the first plate (110) to maintain the shape of the first plate (110). The first plate (110) is a swash plate support bearing of a hydrostatic continuously variable transmission, including an internal core (IW) located between the one surface and the other surface.

13. The swash plate support bearing of the hydrostatic continuously variable transmission according to claim 12, wherein the internal core (IW) is made of a metal material.

14. The swash plate support bearing of the hydrostatic continuously variable transmission according to claim 13, wherein the internal core (IW) is made of a steel material.

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