Bearing for supporting swash plate of hydrostatic transmission

Abstract

The invention relates to a bearing for supporting a swash plate of a hydrostatic transmission. The present invention relates to a technique for fixing to a bracket by bonding plates made of an aluminum material and a Teflon material or forming an additional fixing portion not in contact with the bracket, thereby facilitating control of neutral reset and improving manufacturability and versatility.

Description

Technical Field

[0001] The present invention relates to a bearing for supporting a swash plate in a hydrostatic transmission. Background Art

[0002] Hydrostatic transmissions are installed in working vehicles that frequently change speeds due to their operating characteristics. In particular, hydrostatic transmissions are suitable for agricultural working vehicles (agricultural tractors, combine harvesters, rice transplanters, etc.).

[0003] The hydrostatic transmission changes speed in a stepless manner and is composed of a hydraulic motor and a hydraulic pump.

[0004] The hydraulic motor generates a rotational force on an output shaft using hydraulic pressure based on the flow rate of the working fluid from the hydraulic pump.

[0005] The hydraulic pump operates by utilizing the rotational force output by the engine, sucks in a 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 utilizing the hydraulic pressure from the hydraulic pump.

[0006] The hydraulic pump is provided with a swash plate for speed change, and the speed change is performed as the angular position of the swash plate changes through rotation. In addition, forward speed change or reverse speed change can be achieved according to the rotation direction of the swash plate in the neutral position. For example, Figure 1 Various angular positions of the swash plate SP relative to the support (or also referred to as "guide") SB are shown. Figure 1 (a) shows the forward state, Figure 1 (b) shows the neutral (stop) state, Figure 1 (c) shows the retreat state.

[0007] The flow rate supplied to the hydraulic motor varies according to the angular position of the swash plate SP, whereby the hydrostatic transmission performs stepless acceleration and deceleration. That is, the hydraulic pump is a variable capacity hydraulic pump that performs speed change by varying the flow rate supplied to the hydraulic motor. In addition, the degree of capacity change depends on the angular position (rotation direction and rotation amount) of the swash plate SP.

[0008] In recent years, a swash plate SP has been applied to a hydraulic motor in order to make the torque of the output shaft variable.

[0009] When the swash plate SP is rotated to change the angular position of the swash plate SP, a large amount of friction and heat are generated. Therefore, in order to make the swash plate SP rotate smoothly, a metal bearing is installed on the bracket SB. That is, a bearing is provided between the swash plate SP and the bracket SB, rather than the swash plate SP and the bracket SB being in direct contact.

[0010] Normally, the angular position of the swash plate SP is changed in response to a driver's operation.

[0011] Therefore, if there is no operation by the driver, the angular position of the swash plate SP needs to be reset to the neutral reset angle. Here, the neutral reset angle refers to the angular position of the swash plate SP within the range where the output shaft of the hydrostatic transmission can stop by itself. For example, if the swash plate SP is reset within the neutral reset angle, the angular position of the swash plate SP can theoretically be reset to 0 degrees, which is the neutral position, by sliding between the swash plate SP and the bearing.

[0012] However, the friction resistance between the swash plate SP and the bearings hinders the angular position of the swash plate SP from being reset to the neutral position. That is, if the friction resistance between the swash plate SP and the bearings is large, the swash plate SP may have difficulty in being reset 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 operation may be input to the swash plate SP electronically or mechanically. In either case, an instrument structure for inputting a rotational force to the swash plate SP is required.

[0015] The tolerance of the instrument structure needs to be controlled to a degree that enables the swash plate SP to be reset to within the neutral reset angle.

[0016] If the neutral return angle is large, the tolerances of the instrument structure can be controlled somewhat loosely.

[0017] On the contrary, if the neutral return angle is small, the tolerance of the instrument structure needs to be precisely controlled. In addition, if you are not careful, the neutral return of the swash plate SP may fail. All these increase the production unit price.

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

[0019] If a bearing with excellent performance is used, a larger neutral reset angle can be achieved. In addition, if the neutral reset angle is large, tolerance management becomes easier, thereby reducing the production unit price and improving the reliability of the equipment.

[0020] The present invention relates to a bearing, and the existing bearing is further described below.

[0021] like Figure 2 As shown, 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 a 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 installation Figure 2 The coupling relationship between the bracket SB of the bearing 200 and the bearing 200.

[0026] A fixing screw groove FG is formed at a position corresponding to the fixing hole FH in the central region of the bracket SB, and positioning protrusions PP are formed at positions corresponding to the positioning holes PH on both sides of the fixing screw groove FG.

[0027] The fixing screw FS fixes the bearing 200 to the bracket SB using the fixing hole FH and the fixing screw groove FG.

[0028] The fixing screw FS needs to be tightened to make the bearing 200 and the bracket SB fit tightly. That is, there should be no floating space between the bearing 200 and the bracket SB. This is the only way to properly assemble the swash plate SP.

[0029] Normally, the swash plate SP rotates in close contact with the bearing 200. Therefore, if the sliding between the swash plate SP and the bearing 200 is improper, the surface (contact surface) of the first plate 210 is pushed by the friction resistance. That is, the surface of the polytetrafluoroethylene material is pushed by the friction resistance and causes curling. Such a phenomenon is prevented by the positioning protrusions PP that are arranged on both sides of the fixing screw FS and position 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, the manufacturability of the bearing 200 is poor.

[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 embedded so as not to protrude further from the surface of the bearing 200. For this reason, the second plate 220 needs to be able to ensure its depth. Therefore, the thickness of the second plate 220 becomes thicker, and the rigidity is also increased accordingly, so that it is difficult to shape the second plate 220.

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

[0034] Even when the shape of the second plate 220 is completed, the shape of the second plate 220 may be restored due to its own elastic restoring force. In this way, the operation of fixing the bearing 200 to the bracket SB becomes difficult.

[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 roughness of the surface of the bearing 200 is increased due to burrs and the like generated when the holes FH and PH are formed. As a result, scratches and the like are generated on the swash plate SP, and the friction resistance increases. Therefore, it is necessary to grind the surface of the bearing 200 after the hole forming operation is completed. In addition, the productivity is reduced accordingly.

[0037] Fourth, it may not be possible to guarantee the uniformity of specifications for each product.

[0038] For example, the specifications of holes FH and PH may not be completely consistent for each product. In this case, the surface friction coefficient may be different for each product. As a result, the reliability of the product is reduced due to the unevenness of the characteristics of each finished product (swash plate assembly).

[0039] Fifth, there is the inconvenience of needing to form an additional positioning protrusion PP on the bracket SB.

[0040] Sixth, since it is difficult to manage the friction coefficient, the neutral reset angle needs to be small, which requires precise tolerance management or control design of the relevant instrument structure. And, such a situation ultimately increases the production unit price. Summary of the invention

[0041] Problems to be solved by the invention

[0042] The present invention is proposed from the consideration of the technology that can solve the above problems.

[0043] Means for solving problems

[0044] A swash plate supporting bearing of a hydrostatic transmission in a first embodiment of the present invention is combined with a bracket supporting a swash plate used in the hydrostatic transmission, and is arranged between the swash plate and the bracket to reduce the friction generated when the swash plate rotates, and the swash plate supporting bearing includes: a first plate having a contact surface on one side that contacts the swash plate curved surface of the swash plate, and the first plate is made of synthetic resin; and a second plate is circularly curved to have a curvature, and is tightly overlapped with the other side of the first plate to maintain the shape of the first plate, and the second plate is made of metal; the first plate is made of polytetrafluoroethylene.

[0045] Preferably, the second plate may be made of aluminum.

[0046] The thickness of the first plate is 0.36 mm.

[0047] The friction coefficient of the contact surface is controlled to be between 0.003 and 0.005.

[0048] The friction coefficient of the contact surface has a value such that a neutral return angle of the swash plate is 0.8 degrees to 1.5 degrees.

[0049] The first plate has a plurality of inner cores located between the one surface and the other surface, and the plurality of inner cores are made of metal.

[0050] The plurality of inner cores may be configured into a mesh shape.

[0051] The first plate includes: a contact portion having the contact surface; and a first fixed portion, which is bent and extended at both ends of the contact portion across the contact portion and fixed to the bracket; the second plate includes: a combining portion, which is combined with the contact portion; and a second fixed portion, which is bent and extended at both ends of the combining portion across the combining portion and fixed to the bracket together with the first fixed portion; the first fixed portion and the second fixed portion do not contact the swash plate.

[0052] A swash plate supporting bearing of a hydrostatic transmission in a second embodiment of the present invention is combined with a bracket supporting a swash plate used in the hydrostatic transmission, and is arranged between the swash plate and the bracket to reduce the friction generated when the swash plate rotates, and the swash plate supporting bearing includes: a first plate, one side of which has a contact surface that contacts the swash plate curved surface of the swash plate, and the first plate is made of synthetic resin; and a second plate, which is circularly curved to have a curvature and tightly overlaps with the other side of the first plate to maintain the shape of the first plate, and the second plate is made of metal; the first plate has a plurality of inner cores located between the one side and the other side.

[0053] Effects of the Invention

[0054] According to the present invention, the following effects are achieved.

[0055] First, by using the second plate which is thinner than before and made of aluminum, the bearing has excellent manufacturability.

[0056] Second, since the second plate has excellent shape retention, the assemblability is improved.

[0057] Third, since the fixing means is eliminated in the area where the contact surface with the swash plate is located, the productivity of the bearing is improved.

[0058] Fourth, because at least the uniformity of the contact surface is guaranteed, the reliability of the product is improved.

[0059] Fifth, not only is it not necessary to form an additional positioning protrusion on the bracket, but also a long hole is applied, so the versatility of the bearing is improved.

[0060] Sixth, since the required appropriately large neutral reset angle can be obtained, the production unit price can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a reference diagram for explaining the speed change based on the angular position of the swash plate.

[0062] Figure 2 This is a reference diagram for explaining a conventional bearing.

[0063] Figure 3 It is used to illustrate Figure 2 Reference diagram of the bearing and bracket combination relationship.

[0064] Figure 4 It is a schematic three-dimensional view of a bearing according to an embodiment of the present invention.

[0065] Figure 5 yes Figure 4 Schematic exploded view of the bearing.

[0066] Figure 6 yes Figure 4 Cross-sectional photo of the bearing.

[0067] Figure 7 It is used to illustrate Figure 4 Reference diagram of the bearing and bracket combination relationship. DETAILED DESCRIPTION

[0068] Preferred embodiments of the present invention will be described with reference to the accompanying drawings. For the sake of brevity, descriptions of known structures will be omitted or compressed as much as possible.

[0069] Figure 4 1 is a schematic perspective view of a swash plate supporting bearing (hereinafter referred to as a "bearing") 100 of a hydrostatic transmission according to an embodiment of the present invention. Figure 5 yes Figure 4 A schematic exploded view of the bearing 10 is shown.

[0070] Reference Figure 4 and Figure 5 The bearing 100 of this embodiment includes a first plate 110 and a second plate 120 .

[0071] The first plate 110 is made of a synthetic resin material, and more specifically, is made of polytetrafluoroethylene.

[0072] The first plate 110 includes a contact portion 111 and first fixing portions 112 a , 112 b .

[0073] One surface of the contact portion 111 has a contact surface CF that comes into contact with the swash plate SP.

[0074] The contact surface CF contacts the swash plate curved surface having a circular curvature in an arc shape. Therefore, the contact portion 111 is formed in a circularly curved shape to have a curvature matching the shape of the swash plate curved surface.

[0075] The first fixing portions 112a and 112b are fixed to the bracket SB.

[0076] The first fixing portions 112 a and 112 b are extended and formed at both ends of the contact portion 111 .

[0077] The first fixing portions 112a and 112b on both sides are bent and extended at both ends of the contact portion 111 across the contact portion 111. The bending direction is the direction away from the swash plate SP. Therefore, the first fixing portions 112a and 112b do not contact the swash plate SP.

[0078] 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 an aluminum material. Aluminum has excellent processability and shape retention. The second plate 120 serves to enhance rigidity to maintain the shape of the first plate 110 .

[0079] The second plate 120 includes a coupling portion 121 and second fixing portions 122 a , 122 b .

[0080] The coupling portion 121 is coupled to the other surface of the contact portion 111. Therefore, the coupling portion 121 is formed into a circularly curved shape to have a curvature matching 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 swash plate curved surface, and the other surface of the first plate 110 closely overlaps with the second plate 120.

[0081] The second fixing portions 122a and 122b are connected to the first fixing portions 112a and 112b. In addition, the second fixing portions 122a and 122b are fixed to the bracket SB in a state of being connected to the first fixing portions 112a and 112b.

[0082] The second fixing portions 122 a and 122 b are extended and formed at both ends of the coupling portion 121 .

[0083] The second fixing portions 122a and 122b on both sides are bent and extended at both ends of the coupling portion 121 across the coupling portion 121. The bending direction is a direction away from the swash plate SP.

[0084] Therefore, the first fixing portions 112a, 112b and the second fixing portions 122a, 122b are not in contact with the swash plate SP. This means that there is no need to consider the friction resistance between the first fixing portions 112a, 112b and the swash plate SP.

[0085] The first plate 110 and the second plate 120 have the same shape and are overlapped and coupled to each other.

[0086] On the other hand, refer to Figure 6According to the cross-sectional photograph of FIG. 1 , the thickness of the first plate 110 is about 0.36 mm, and the thickness of the second plate 120 is about 0.92 mm.

[0087] Through a large number of experiments, it is confirmed that the thicker the first plate 110 is, the greater the friction coefficient of the contact surface CF becomes. In the past, the friction coefficient of the contact surface CF was controlled within the range of 0.010 to 0.020. However, as in this embodiment, when the thickness of the first plate 110 is 0.36 mm, the friction coefficient of the contact surface CF is reduced to 0.003. However, it is observed that when the thickness of the first plate 110 is less than 0.36 mm, the durability of the bearing 100 is reduced.

[0088] The friction coefficient of the contact surface CF is related to the neutral return angle.

[0089] If the friction coefficient of the contact surface CF is 0.010 or more as in the prior art, the neutral return angle is 0.3 to 0.5 degrees. On the contrary, if the friction coefficient of the contact surface CF is 0.003 as in the present embodiment, the neutral return angle is 0.8 degrees or more. This means that in the case of the present embodiment, the design for returning the swash plate SP to the neutral position becomes simple. According to the experiment conducted on the embodiment to which the present invention is applied, it is confirmed that even if the friction coefficient of the contact surface CF is 0.005, the neutral return angle can be maintained larger than 0.8 degrees.

[0090] Of course, if the neutral return angle is too large, the neutral departure angle also becomes large. Here, the neutral departure angle refers to the angular position of the swash plate SP at which the output shaft responds and rotates when the swash plate SP at the neutral position rotates.

[0091] For example, if the neutral departure angle is large, the response of the output shaft based on the driver's operation becomes slow. In particular, in most cases, the neutral departure 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 departure angle also increases proportionally. Therefore, in the present 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 degrees to 1.5 degrees.

[0092] According to the present embodiment, the thickness of the second plate 120 is 0.92 mm, which is about half the thickness of the conventional plate. Such a thin thickness is achieved because the additional fixing portions 112a, 112b, 122a, 122b are provided in the region where the bearing 100 does not contact the swash plate SP. That is, since the bearing 100 is coupled to the bracket SB using the additional fixing portions 112a, 112b, 122a, 122b that do not contact the swash plate SP, the thickness of the second plate 120 can be significantly reduced.

[0093] As described above, since the second plate 120 can be thin, the moldability of the bearing 100 is further improved. In addition, since the aluminum material is not only lighter but also has excellent shape retention, the assembly performance of the bearing 100 to the bracket SB is also improved.

[0094] Re-reference Figure 6 It can be confirmed that a plurality of inner cores IW are arranged on the first plate 110 .

[0095] The inner core IW is used to prevent the first plate 110 from being pushed and curled due to friction with the swash plate SP. To this end, 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 steel material with excellent rigidity. The inner core IW plays a role in supporting the first plate 110 so that the first plate 110 will not be pushed even if friction resistance is generated between the rotating swash plate SP and the contact surface CF.

[0096] As described above, the plurality of inner cores IW support the first plate 110 to prevent the first plate 110 from curling, and thus according to the present invention, no additional positioning holes PH or positioning protrusions PP are required.

[0097] The plurality of inner cores IW may be designed to be arranged in a mesh shape. The mesh shape arrangement may enable the plurality of inner cores IW to maintain the shape of the first plate 110 and be protected from friction forces that may be applied from different directions. On the other hand, fixing holes FH are formed in the first fixing portions 112a, 112b and the second fixing portions 122a, 122b.

[0098] The bearing 100 of the present invention is used in a structure that supports a swash plate SP of a hydrostatic transmission.

[0099] In a hydrostatic transmission, a hydraulic pump and a hydraulic motor are provided in pairs. A swash plate SP is provided in the hydraulic pump and, in recent years, also in the hydraulic motor.

[0100] like Figure 7 As shown in the reference figures of , generally, the swash plate SP is arranged to be supported by a bracket SB.

[0101] However, since the swash plate SP rotates, friction may be generated between the rotating swash plate SP and the bracket SB when the swash plate SP rotates. Therefore, in order to reduce the friction, it is necessary to provide the bearing 100 between the swash plate SP and the bracket SB.

[0102] According to the present embodiment, a fixing screw groove FG is formed at a position of the bracket SB corresponding to the fixing hole FH. Therefore, the bearing 100 can be fixed to the bracket SB by the fixing screw FS. Therefore, the contact portion 111 and the coupling portion 121 may not have a fixing means for fixing to the bracket SB.

[0103] The fixing screws FS fix the bearing 100 to the bracket SB in the areas on both sides of the disengagement contact surface CF. Therefore, the fixing screws FS can also play a role in preventing the contact surface CF from being pushed in the entire area of ​​the contact surface CF that rubs against the swash plate SP. Of course, as described above, although the contact surface CF is prevented from being pushed in by the plurality of inner cores IW, the preventing function is further enhanced by the fixing screws FS.

[0104] In addition, the fixing hole FH has a long hole shape formed substantially in a direction perpendicular to the line segment connecting the two fixing holes FH. Even if the specifications of the bracket SB are slightly different, the long hole-shaped fixing hole FH can properly fix the bearing 100 to the bracket SB. As described above, by forming the long hole-shaped fixing hole FH and not additionally providing the positioning protrusion PP on the bracket SB, the versatility of the bearing 100 is improved.

[0105] On the other hand, the present invention mainly has the following features: the second plate 120 is made of aluminum and is relatively thin; the bearing 100 is coupled to the bracket SB at both ends of the bearing 100 that are not in contact with the swash plate SP; and the first plate 110 is provided with a plurality of inner cores IW. Furthermore, these three features can be applied to the bearing 100 individually or selectively, or can be applied to the bearing 100 together as in the above-mentioned embodiment.

[0106] The above embodiments are only for describing the preferred embodiments of the present invention, and various application forms are possible. Therefore, it should not be interpreted that the present invention is limited to the above-mentioned contents. On the contrary, the scope of rights of the present invention should be understood as the claims and their equivalents recorded separately.

Claims

1. A swash plate supporting bearing for a hydrostatic transmission, the swash plate supporting bearing (100) being coupled to a bracket (SB) supporting a swash plate (SP) used in the hydrostatic transmission, and being arranged to reduce friction between the swash plate (SP) and the bracket (SB) when the swash plate (SP) rotates, wherein: The swash plate supporting bearing (100) comprises: a first plate (110) having a contact surface (CF) on one side for contacting the swash plate curved surface of the swash plate (SP), the first plate (110) being made of synthetic resin; and The second plate (120) is in a circularly curved shape to have a curvature and is closely overlapped with the other surface of the first plate (110) to maintain the shape of the first plate (110), and the second plate (120) is made of metal; The first plate (110) is made of polytetrafluoroethylene.

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

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

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

005.

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

6. The swash plate supporting bearing of a hydrostatic transmission according to claim 1, wherein: The first plate (110) has a plurality of inner cores (IW) located between the one surface and the other surface; The plurality of inner cores (IW) are made of metal.

7. The swash plate supporting bearing of a hydrostatic transmission according to claim 6, wherein: The plurality of inner cores (IW) are configured in a mesh shape.

8. The swash plate supporting bearing of a hydrostatic transmission according to claim 1, wherein: The first plate (110) comprises: a contact portion (111) having the contact surface (CF); and A first fixing portion (112a, 112b) is bent and extended at both ends of the contact portion (111) across the contact portion (111), and is fixed to the bracket (SB); The second plate (120) comprises: a bonding portion (121) bonded to the contact portion (111); and A second fixing portion (122a, 122b) is bent and extended at both ends of the combining portion (121) across the combining portion (121), and is fixed to the bracket (SB) together with the first fixing portion (112a, 112b); The first fixing portion (112a, 112b) and the second fixing portion (122a, 122b) do not contact the swash plate (SP).

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

10. The swash plate supporting bearing of a hydrostatic transmission according to claim 9, wherein: The fixing hole (FH) is a long hole.

11. The swash plate supporting bearing of a hydrostatic transmission according to claim 8, wherein: The contact portion (111) and the coupling portion (121) do not have fixing means for fixing to the bracket (SB).

12. A swash plate supporting bearing for a hydrostatic transmission, the swash plate supporting bearing (100) being coupled to a bracket (SB) supporting a swash plate (SP) used in the hydrostatic transmission, and being arranged to reduce friction between the swash plate (SP) and the bracket (SB) when the swash plate (S) rotates, wherein: The swash plate supporting bearing (100) comprises: a first plate (110) having a contact surface (CF) on one side for contacting the swash plate curved surface of the swash plate (SP), the first plate (110) being made of synthetic resin; and The second plate (120) is in a circularly curved shape to have a curvature and is closely overlapped with the other surface of the first plate (110) to maintain the shape of the first plate (110), and the second plate (120) is made of metal; The first plate (110) has a plurality of inner cores (IW) located between the one surface and the other surface.

13. The swash plate supporting bearing of a hydrostatic transmission according to claim 12, wherein: The plurality of inner cores (IW) are made of metal.

14. The swash plate supporting bearing of a hydrostatic transmission according to claim 13, wherein: The plurality of inner cores (IW) are made of steel.

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