bearing for supporting the swashplate of a 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 its operating characteristics. In particular, hydrostatic continuously variable transmissions are appropriately applied to agricultural work vehicles (such as agricultural tractors, combines, rice transplanters, etc.).

[0003] A 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 supplies it to the hydraulic motor. That is, the hydraulic pump supplies hydraulic pressure to the hydraulic motor, and the hydraulic motor operates by the hydraulic pressure coming from the hydraulic pump.

[0006] The hydraulic pump has a swash plate for shifting gears, and the gear shift is performed by changing the angular position of the swash plate by rotation. Also, forward or reverse gear shifts can be made 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 a support (or also referred to as a "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 continuously performs speed increase and decrease by changing the flow rate provided to the hydraulic motor depending on the angular position of the swash plate SP. That is, the hydraulic pump is configured as a variable displacement type that executes gear 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] Furthermore, in recent years, swashplate springs (SPs) are sometimes applied to hydraulic motors to vary the torque (toque) of the output shaft.

[0009] Significant friction and heat are generated during the rotation of the swash plate SP to change its angular position. Therefore, a metal bearing is installed in the support section SB to ensure smooth rotation of the swash plate SP. In other words, the swash plate SP does not directly contact the support section SB; rather, a bearing is interposed between the swash plate SP and the support section SB.

[0010] Generally, the angular position of the swashplate SP is changed by the driver's operation.

[0011] Therefore, without driver intervention, 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 in which the output shaft of the hydrostatic continuously variable transmission can stop on its own. For example, when the swash plate SP returns to within the neutral return angle, the friction between the swash plate SP and the bearings can theoretically return the angular position of the swash plate SP to the neutral position of 0 degrees.

[0012] Incidentally, the frictional resistance between the swash plate SP and the bearing acts as an obstacle to returning the swash plate SP's angular position to the neutral position. In other words, 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] Frictional resistance can vary depending on the shape and material of the bearing.

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

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

[0016] If the neutral return angle is large, then the tolerances of the mechanical structure can be managed a little more broadly.

[0017] On the other hand, if the neutral return angle is small, the tolerances of the mechanical structure must also be precisely controlled. Furthermore, defects may occur in the neutral return of the swash plate spring. And all of these issues lead to increased production costs.

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

[0019] If a high-performance bearing is used, the neutral return angle can be increased accordingly. A larger neutral return angle makes tolerance control easier, reduces production costs, and improves the reliability of the equipment.

[0020] Since this invention relates to bearings, conventional bearings will be explained in more detail below.

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

[0022] The first plate 210 is made of polytetrafluoroethylene (commonly known as "Teflon®").

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

[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] Figure 3 shows the connection between the support part SB, where the bearing 200 shown in Figure 2 is mounted, 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 being closely adhered 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 where 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 should not interfere with each other. Therefore, the head of the fixing screw FS needs to be deeply pushed in so as not to protrude beyond the surface of the bearing 200. For this purpose, the second plate 220 has to ensure that depth. For this reason, the thickness of the second plate 220 increases, and the rigidity increases accordingly, making it difficult to manufacture the shape of the second plate 220.

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

[0034] Even if the shape of the second plate 220 is manufactured, the shape of the second plate 220 may be restored by its own elastic restoring force. In that case, the process of fixing the bearing 200 to the support part SB becomes somewhat complicated.

[0035] Third, the productivity of bearing 200 will decrease.

[0036] Three holes, FH and PH, are formed in bearing 200. Burrs and other debris generated during the formation of holes FH and PH worsen the surface roughness of bearing 200. This causes scratches on the swash plate SP, increasing frictional resistance, so the surface of bearing 200 must be finished to be smooth after the hole formation process is complete. Furthermore, this reduces productivity.

[0037] Fourth, it may not always be possible to guarantee uniformity of specifications across different products.

[0038] For example, the hole FH and PH specifications may not be precisely consistent across products. In this case, the surface friction coefficient may differ from product to product. This inconsistency in characteristics between finished products (swashplate assemblies) reduces the reliability of the product.

[0039] Fifth, it involves the inconvenience of having to form a separate positioning projection PP on the support part SB.

[0040] Sixth, because controlling the coefficient of friction is difficult and the neutral return angle needs to be small, precise tolerance control and control design of related mechanical structures are required. Ultimately, these factors increase production costs. [Overview of the Initiative] [Problems that the invention aims to solve]

[0041] This invention was devised to provide a technology that can solve the aforementioned problems. [Means for solving the problem]

[0042] A swash plate support bearing for a hydrostatic continuously variable transmission according to a first 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 when the swash plate rotates, and comprises a first plate made of synthetic resin material having a contact surface on one side that contacts the curved surface of the swash plate, and a second plate made of metal material having a rounded shape with curvature, which overlaps closely with the other side of the first plate to maintain the shape of the first plate, wherein the first plate is made of polytetrafluoroethylene material.

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

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

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

[0046] The coefficient of friction of the contact surface is such that the neutral return angle of the swash plate is between 0.8 degrees and 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 metal.

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

[0049] The first plate includes a contact portion having the contact surface and a first fixing portion that extends from both ends of the contact portion, sandwiching the contact portion, and is fixed to the support portion. The second plate includes a connecting portion that is coupled to the contact portion and a second fixing portion that extends from both ends of the connecting portion, sandwiching the connecting portion, and is fixed to the support portion together with the first fixing portion. The first fixing portion and the second fixing portion do not come into contact with the slanted plate.

[0050] A swash plate support bearing for a hydrostatic continuously variable transmission according to a 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 when the swash plate rotates, and includes a first plate of synthetic resin material having a contact surface on one side that contacts the curved surface of the swash plate, and a second plate of metal material having a rounded shape with curvature and overlapping in close contact with the other side of the first plate to maintain the shape of the first plate, wherein the first plate includes an internal core located between the one side and the other side. [Effects of the Invention]

[0051] The present invention has the following effects.

[0052] Firstly, by using a second aluminum plate, which is thinner than conventional materials, the bearing can be manufactured more easily.

[0053] Secondly, the shape retention of the second plate is good, which improves ease of assembly.

[0054] Thirdly, since the fixing means are removed from the area where the contact surface contacts the swash plate, the productivity of bearings is improved.

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

[0056] Fifth, not only is it unnecessary to form separate positioning protrusions on the support portion, but the application of elongated holes improves the versatility of the bearing.

[0057] Sixth, since a sufficiently large neutral return angle can be obtained as desired, production costs can be reduced. [Brief explanation of the drawing]

[0058] [Figure 1] This is a reference diagram to explain how speed changes are affected by the angle of the swash plate. [Figure 2]This is a reference diagram to explain conventional bearings. [Figure 3] Figure 2 is a reference diagram illustrating the connection between the bearing and the support. [Figure 4] This is a schematic perspective view of a bearing according to one embodiment of the present invention. [Figure 5] Figure 4 is a schematic exploded view of the bearing. [Figure 6] Figure 4 is a cross-sectional photograph of the bearing. [Figure 7] Figure 4 is a reference diagram illustrating the connection between the bearing and the support. [Modes for carrying out the invention]

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

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

[0061] Referring to Figures 4 and 5, the bearing 100 according to this 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] The contact portion 111 has a contact surface CF on one side that contacts the swash plate SP.

[0065] The contact surface CF contacts the swash plate surface, which has a rounded, arc-shaped curve. Therefore, the contact portion 111 is manufactured in a rounded shape so as to have a curvature corresponding to the shape of the swash plate surface.

[0066] The first fixing parts 112a and 112b are fixed to the support part 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 in between. The direction of bending is away from the swash plate SP. Therefore, the first fixing portions 112a and 112b do not come into contact with the swash plate SP.

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

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

[0071] The connecting portion 121 is joined to the other surface of the contact portion 111. Therefore, the connecting portion 121 is manufactured in a rounded shape with a curvature corresponding to the shape of the contact portion 111. In other words, according to this embodiment, one surface of the first plate 110 has a contact surface CF that contacts the curved surface of the swash plate, and the other surface of the first plate 110 overlaps closely with the second plate 120.

[0072] The second fixing parts 122a and 122b are connected to the first fixing parts 112a and 112b. Furthermore, the second fixing parts 122a and 122b are fixed to the support part SB while connected to the first fixing parts 112a and 112b.

[0073] The second fixing parts 122a and 122b extend from both ends of the connecting part 121.

[0074] The second fixing parts 122a and 122b on both sides extend outwards from both ends of the connecting part 121, flanking the connecting part 121. The direction of bending is away from the swash plate SP.

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

[0076] The first plate 110 and the second plate 120 have the same shape and are joined together by overlapping each other.

[0077] On the other hand, referring to the cross-sectional photograph in Figure 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] Numerous experiments have confirmed that the coefficient of friction of the contact surface CF gradually increases as the thickness of the first plate 110 increases. Conventionally, the coefficient of friction of the contact surface CF was controlled within the range of 0.010 to 0.020. However, in this embodiment, when the thickness of the first plate 110 is 0.36 mm, the coefficient of friction of the contact surface CF decreases to 0.003. However, it was observed that the durability of the bearing 100 decreases if the thickness of the first plate 110 is less than 0.36 mm.

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

[0080] If the friction coefficient of the contact surface CF is set to 0.010 or higher, as in the conventional method, the neutral return angle will be 0.3 to 0.5 degrees. On the other hand, if the friction coefficient of the contact surface CF is set to 0.003, as in this embodiment, the neutral return angle will be 0.8 degrees or higher. This means that, in this embodiment, the design for returning the swash plate SP to the neutral position becomes simpler. Experiments using an embodiment to which the present invention is applied confirmed that even when the friction coefficient of the contact surface CF is 0.005, the neutral return angle can be maintained at a value greater than 0.8 degrees.

[0081] Of course, if the neutral return angle is too large, the neutral starting angle will also be large. 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, which was in the neutral position, rotates.

[0082] For example, if the neutral starting angle is large, the response 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 if the neutral return angle is too large, the neutral starting angle will also increase proportionally. Accordingly, in this invention, the friction coefficient of the contact surface CF is controlled to 0.003 to 0.005, and the neutral return angle is controlled to 0.8 to 1.5 degrees.

[0083] In this embodiment, the thickness of the second plate 120 is 0.92 mm. This is about half the thickness of conventional plates. The reason why the thickness can be reduced in this way is that the bearing 100 has separate fixing parts 112a, 112b / 122a, 122b in the area where it does not come into contact with the swash plate SP. In other words, since the bearing 100 is coupled to the support part SB by separate fixing parts 112a, 112b / 122a, 122b that are not involved in contact with the swash plate SP, the thickness of the second plate 120 can be significantly reduced.

[0084] In this way, the thickness of the second plate 120 can be reduced, which further improves the moldability of the bearing 100. Furthermore, because it is made of aluminum, it is not only lighter but also has good shape retention, improving the ease of assembly when mounting the bearing 100 to the support part SB.

[0085] Furthermore, referring to Figure 6, it can be confirmed that the internal core IW is located on the first plate 110.

[0086] The internal core IW is intended to prevent the first plate 110 from being pressed and wound due to friction with the swash plate SP. For this reason, the internal core IW needs to be made of a material with higher rigidity than the first plate 110. More specifically, in this embodiment, the internal core IW is made of a metal material. In particular, the internal core IW can be made of a highly rigid steel material. The internal core IW plays a role in supporting the first plate 110 so that it is not pressed even if frictional resistance is generated between the rotating swash plate SP and the contact surface CF.

[0087] In this way, the internal core IW supports the first plate 110 so that it does not get rolled up, so according to the present invention, separate positioning holes PH and positioning protrusions PP are not required.

[0088] The internal core IW can be designed to be arranged in a mesh pattern. This mesh arrangement allows the internal core IW to maintain the shape of the first plate 110 against frictional forces applied in various directions. Meanwhile, fixing holes FH are formed in the first fixing parts 112a, 112b and the second fixing parts 122a, 122b.

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

[0090] A hydrostatic continuously variable transmission (CVT) is equipped with a pair of hydraulic pumps and hydraulic motors. The swash plate SP is attached to the hydraulic pump, and around this time, it is sometimes also attached to the hydraulic motor.

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

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

[0093] In this embodiment, the support portion SB has a fixing screw hole FG 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 reason, the contact portion 111 and the connecting portion 121 do not need to be provided with fixing means for fixing to the support portion SB.

[0094] The fixing screw FS secures the bearing 100 to the support part SB in the areas on both sides away from the contact surface CF. Therefore, the fixing screw FS also serves to prevent the contact surface CF from being pushed in all areas of the contact surface CF where friction with the swash plate SP occurs. Of course, as mentioned above, the internal core IW also prevents the contact surface CF from being pushed in, but the fixing screw FS further reinforces this anti-pull function.

[0095] Furthermore, the fixing holes FH have the shape of elongated holes that are approximately perpendicular to the line segment connecting the two fixing holes FH. The elongated fixing holes FH allow the bearing 100 to be properly and securely installed on the support part SB even if the specifications of the support part SB are slightly different. Thus, the versatility of the bearing 100 is improved by forming the elongated fixing holes FH and by not providing a separate positioning projection PP on the support part SB.

[0096] On the other hand, the present invention has the following characteristics: the second plate 120 is made of aluminum and has a thin thickness; the bearing 100 is connected to the support part SB at both ends of the bearing 100 that do not come into contact with the swash plate SP; and the first plate 110 is provided with an internal core IW. These three major characteristics can be applied to the bearing 100 individually or selectively, or they can be applied to the bearing 100 together, as in the above embodiment.

[0097] The embodiments described above are merely preferred examples of the present invention, and it can have a variety of applications. Therefore, the present invention should not be understood to be limited to the content described above. Instead, the scope of the rights of the present invention should be understood in accordance with the claims and equivalents described separately.

Claims

1. A swash plate support bearing (100) is provided between the swash plate (SP) and the support part (SB) of a hydrostatic continuously variable transmission, and is coupled to the support part (SB) that supports the swash plate (SP), in order to reduce friction generated when the swash plate (SP) rotates. A first plate (110) made of synthetic resin material having a contact surface (CF) on one side that contacts the curved surface of the inclined plate (SP), It includes a second plate (120) made of a metal material having a rounded shape with curvature, which 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 made of polytetrafluoroethylene material. The first plate (110) is, The contact portion (111) having the contact surface (CF), The first fixing portion (112a, 112b) extends from both ends of the contact portion (111) with the contact portion (111) in between, and is fixed to the support portion (SB), The second plate (120) is, A coupling portion (121) coupled to the contact portion (111), The system includes the aforementioned joint (121), with the second fixing portion (122a, 122b) extending from both ends of the joint (121) and fixed to the support portion (SB) together with the first fixing portion (112a, 112b), The first fixing portion (112a, 112b) and the second fixing portion (122a, 122b) do not come into contact with the swash plate (SP). A bearing for supporting the swash plate of a hydrostatic continuously variable transmission, wherein fixing holes (FH) are formed in the first fixing portion (112a, 112b) and the second fixing portion (122a, 122b).

2. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 1, wherein the second plate (120) is made of aluminum.

3. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 1, wherein the thickness of the first plate (110) is 0.36 mm.

4. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 1, wherein the coefficient of friction of the contact surface (CF) is 0.003 to 0.

005.

5. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 4, wherein the coefficient of friction of the contact surface (CF) is such that the neutral return angle of the swash plate is 0.8 degrees to 1.5 degrees.

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

7. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 6, wherein the internal core (IW) is arranged in a mesh pattern.

8. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 1, wherein the fixing hole (FH) is an elongated hole.

9. The bearing for supporting the swash plate of a hydrostatic continuously variable transmission according to claim 1, wherein the contact portion (111) and the coupling portion (121) do not include fixing means for fixing to the support portion (SB).

10. A swash plate support bearing (100) is provided between the swash plate (SP) and the support part (SB) of a hydrostatic continuously variable transmission, and is coupled to the support part (SB) to reduce friction generated when the swash plate (S) rotates. One side of the first plate (110) made of synthetic resin material includes a contact surface (CF) that contacts the curved surface of the inclined plate (SP), It includes a second plate (120) made of a metal material having a rounded shape with curvature, which 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) includes an internal core (IW) located between the one surface and the other surface. The second plate (120) is made of aluminum, The aforementioned internal core (IW) is made of steel, and it is a bearing for supporting the swash plate of a hydrostatic continuously variable transmission.

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