Load-controlled hydraulic supply for an attachment attached to an agricultural tractor

Abstract

A load-controlled hydraulic supply for an attachment attached to an agricultural tractor includes a hydraulic high-pressure source providing a volume flow in a supply line, a pressure-compensated control valve including an actuation device for adjusting the volume flow in the supply line, a return line leading to a hydraulic reservoir, and a load-indicating line. The volume flow is adjusted based on pressure feedback prevailing at the load-indicating line.

Claims

1. A load-controlled hydraulic supply for an attachment attached to an agricultural tractor, comprising: a hydraulic high-pressure source providing a volume flow in a supply line; a pressure-compensated control valve for adjusting the volume flow in the supply line; a return line leading to a hydraulic reservoir; a load-indicating line; and a valve arrangement for variably increasing a load-indicating pressure prevailing externally at the load-indicating line; wherein the volume flow is adjusted based on pressure feedback prevailing at the load-indicating line; wherein the valve arrangement comprises a first 2/2-way valve which is pilot-actuated via the externally prevailing load-indicating pressure, wherein the first 2/2-way valve is connected on the inlet side to the hydraulic high-pressure source and is prestressed into its open position via an actuating force of a spring element that assists the pilot actuation.

2. The hydraulic supply of claim 1, wherein the load-indicating line is connected to a device for pressure limiting that is movable between an open position and a closed position.

3. The hydraulic supply of claim 2, wherein the device for pressure limiting comprises one of a pressure-limiting valve leading into the hydraulic reservoir or a pressure-reducing valve located in the load-indicating line.

4. The hydraulic supply of claim 3, wherein the pressure-limiting valve communicates with the load-indicating line via a series-connected flow-limiting element.

5. The hydraulic supply of claim 2, wherein the device for pressure limiting comprises a pressure-limiting valve leading into the hydraulic reservoir.

6. The hydraulic supply of claim 5, wherein the pressure-limiting valve communicates with the load-indicating line via a series-connected flow-limiting element.

7. The hydraulic supply of claim 2, wherein the device for pressure limiting comprises a pressure-reducing valve located in the load-indicating line.

8. The hydraulic supply of claim 2, wherein the device for pressure limiting is adjustable with regard to a predetermined pressure threshold value.

9. The hydraulic supply of claim 1, wherein an enable valve designed as a second 2/2-way valve is connected in series with the first 2/2-way valve, wherein the second 2/2-way valve is pilot-actuated via the externally prevailing load-indicating pressure in such a manner that the second 2/2-way valve takes up an open position when a predetermined pressure threshold value is exceeded.

10. A load-controlled hydraulic supply for an attachment attached to an agricultural tractor, comprising: a hydraulic high-pressure source providing a volume flow in a supply line; a pressure-compensated control valve for adjusting the volume flow in the supply line; a return line leading to a hydraulic reservoir; a load-indicating line connected to a device for pressure limiting including a pressure-limiting valve leading into the hydraulic reservoir; and a valve arrangement for variably increasing a load-indicating pressure prevailing externally at the load-indicating line; wherein the volume flow is adjusted based on pressure feedback prevailing at the load-indicating line; wherein the valve arrangement comprises a first 2/2-way valve which is pilot-actuated via the externally prevailing load-indicating pressure, wherein the first 2/2-way valve is connected on the inlet side to the hydraulic high-pressure source and is prestressed into its open position via an actuating force of a spring element that assists the pilot actuation.

11. The hydraulic supply of claim 10, wherein the pressure-limiting valve communicates with the load-indicating line via a series-connected flow-limiting element.

12. The hydraulic supply of claim 11, wherein the series-connected flow-limiting element includes an orifice.

13. The hydraulic supply of claim 10, wherein the device for pressure limiting is adjustable with regard to the predetermined pressure threshold value.

14. The hydraulic supply of claim 10, wherein an enable valve designed as a second 2/2-way valve is connected in series with the first 2/2-way valve, wherein the second 2/2-way valve is pilot-actuated via the externally prevailing load-indicating pressure in such a manner that the second 2/2-way valve takes up an open position when a predetermined pressure threshold value is exceeded.

15. A load-controlled hydraulic supply for an attachment attached to an agricultural tractor, comprising: a hydraulic high-pressure source providing a volume flow in a supply line; a pressure-compensated control valve for adjusting the volume flow in the supply line; a return line leading to a hydraulic reservoir; and a load-indicating line; wherein the volume flow is adjusted based on pressure feedback prevailing at the load-indicating line; wherein a pressure-reducing valve is located in the load-indicating line.

16. The hydraulic supply of claim 15, wherein the pressure-reducing valve is adjustable with regard to a predetermined pressure threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The load-controlled hydraulic supply according to the disclosure for an attachment attached to an agricultural tractor will be described in more detail below with reference to the drawings. Here, identical reference signs relate to corresponding components or components which are of comparable function. In the drawings:

(2) FIG. 1 shows a schematically illustrated first exemplary embodiment of the load-controlled hydraulic supply according to the disclosure; and

(3) FIG. 2 shows a schematically illustrated second exemplary embodiment of the load-controlled hydraulic supply according to the disclosure.

DETAILED DESCRIPTION

(4) The embodiments or implementations disclosed in the above drawings and the following detailed description are not intended to be exhaustive or to limit the present disclosure to these embodiments or implementations.

(5) The hydraulic supply 10 which is schematically illustrated in FIG. 1 serves for operating an attachment 14 attached to an agricultural tractor 12, more specifically for operating at least one hydraulic actuator 18 which is included by an attachment-side hydraulic system 16 and is in the form of an actuating and/or drive device 20, depicted representatively as a hydraulic motor and via which an associated working function of the attachment 14 can be carried out.

(6) The load-controlled hydraulic supply 10 forms what is referred to as a power-beyond interface with a total of four hydraulic ports: Psupply port LSload-indicating port for pressure feedback Rreturn port Ddrainage port

(7) Each of the hydraulic ports P, LS, R and D merges into an associated hydraulic line, more specifically into a supply line 24, which is fed by a hydraulic high-pressure source 22, a load-indicating line 26 and a return or drainage line 30, 32 leading into a hydraulic reservoir 28.

(8) The return port R, like the drainage port D, serves merely for the hydraulic fluid to flow back into the hydraulic reservoir 28 of the agricultural tractor 12; the two ports will therefore not be discussed further here. The focus is rather on the supply port and on the load-indicating port P, LS since these ports are crucial for the actual functioning of the load-controlled hydraulic supply 10. A volume flow adapted in accordance with the load-indicating pressure prevailing at the return-indicating port LS is thus provided by the hydraulic high-pressure source 22, which is a variable displacement pump 34 fed from the hydraulic reservoir 28, via the supply port P.

(9) In other words, the load-controlled hydraulic supply 10 forms what is referred to as a load-sensing system which provides a volume flow, which passes through the supply line 24 in the direction of the supply port P, in accordance with pressure feedback prevailing at the load-indicating line 26.

(10) The attachment-side hydraulic system 16 provided for operating the at least one hydraulic actuator 18 is connected releasably to the load-controlled hydraulic supply 10 via associated hydraulic hoses or hydraulic couplers 36, 38, 40, 42.

(11) Furthermore, in the supply line 24 there is a pressure-compensated control valve 44 with a first actuation device 46 for adjusting the volume flow.

(12) The pressure-compensated control valve 44 is formed from a combination of a 2/2-way proportional valve 48 with a pressure-regulating valve 50, wherein the pressure-regulating valve 50 compares an outlet-side hydraulic pressure with an inlet-side hydraulic pressure at the 2/2-way proportional valve 48 and sets the outlet-side hydraulic pressure to a fixed differential pressure. Thus, the 2/2-way proportional valve 48 keeps the volume flow emerging from its respective open position substantially constant even in the event of load fluctuations of the at least one hydraulic actuator 18 and/or of operationally induced pressure fluctuations within the hydraulic supply 10. To predetermine the volume flow, the 2/2-way proportional valve 48 can be brought into its open position by electrical activation of the first actuation device 46 counter to a restoring force produced via a spring element 52.

(13) Attachments equipped with hydraulic actuators frequently transmit an excessive load-indicating pressure, i.e. which is inappropriate for the actual supply requirements, to the hydraulic supply 10 via the load-indicating line 26. This leads ultimately to the hydraulic supply 10 being caused to generate, and to provide to the supply port P via the supply line 24, a supply pressure exceeding the actual requirements of the hydraulic actuators. In order to prevent the associated losses in efficiency during operation of the hydraulic supply 10, the load-indicating line 26 is connected to a device for pressure limiting 54. The extent of the pressure limiting is adapted here to the anticipated hydraulic supply requirements of the hydraulic actuators and is conventionally specific to each attachment model.

(14) According to the first exemplary embodiment of the load-controlled hydraulic supply that is reproduced in FIG. 1, the device for pressure limiting 54 comprises a pressure-limiting valve 56 leading into the hydraulic reservoir 28.

(15) The pressure-limiting valve 56 is connected on the inlet side to the load-indicating line 26 and is connected on the outlet side to the hydraulic reservoir 28. When a predetermined pressure threshold value is exceeded, the pressure-limiting valve takes up an open position counter to a restoring force generated via a spring element 58, and therefore pressure is correspondingly relieved by hydraulic fluid flowing off out of the load-indicating line 26 in the direction of the hydraulic reservoir 28.

(16) In order to prevent a sudden or uncontrolled drop in pressure in the load-indicating line 26 when the pressure-limiting valve 56 is opened, it is provided that the pressure-limiting valve 56 communicates with the load-indicating line 26 via a series-connected flow-limiting element 60. For example, the flow-limiting element 60 in the form of an orifice 62 is connected in the load-indicating line 26 upstream of the pressure-limiting valve 56, but may also be connected downstream of the pressure-limiting valve 56.

(17) According to a second exemplary embodiment of the load-controlled hydraulic supply according to the disclosure that is reproduced in FIG. 2, the device for pressure limiting 54 comprises, instead of a pressure-limiting valve 56, a pressure-reducing valve 64 located in the load-indicating line 26.

(18) The two exemplary embodiments correspond with regard to the remaining components.

(19) The pressure-reducing valve 64 is prestressed into an open position under the action of a restoring force generated via a spring element 66 and, when a predetermined pressure threshold value on the outlet side is exceeded, is forced into a closed position so that further passage of hydraulic fluid is prevented.

(20) Both the pressure-limiting valve 56 and the pressure-reducing valve 64 are adjustable with respect to the predetermined pressure threshold value via a respective second actuation device 68. For this purpose, the second actuation device 68 is designed in such a manner that the restoring force of the spring element 58, 66 can be influenced in a targeted way by electrical activation of the second actuation device 68.

(21) The pressure threshold value is predetermined individually depending on the respective attachment model and is typically of the order of magnitude of 100 to 190 bar.

(22) The above-described measures satisfy operating situations in which an oversupply of the at least one actuator 18 with hydraulic fluid occurs because of mismatches between the load-controlled hydraulic supply 10 and the attachment-side hydraulic system 16. On the other hand, operating situations leading to an undersupply are also possible, especially whenever an insufficient load-indicating pressure is transmitted to the hydraulic supply 10 of the agricultural tractor 12. Accordingly, there is a valve arrangement 70 for variably increasing a load-indicating pressure prevailing externally at the load-indicating line 26, i.e. at the load-indicating port LS, the valve arrangement making it possible to raise the load-indicating pressure to a level leading to an appropriate volume flow, typically by up to 40 bar.

(23) For this purpose, the valve arrangement 70 comprises a 2/2-way valve 72 which is pilot-actuated via the externally prevailing load-indicating pressure, wherein the 2/2-way valve 72 is connected on the inlet side to the hydraulic high-pressure source 22 and is prestressed into its open position via an actuating force of a spring element 74 that assists the pilot actuation. The 2/2-way valve 72 therefore forms a booster valve with which the extent of the increase in pressure arises directly from the respective actuating force of the spring element 74. On the outlet side, a pilot actuation of the 2/2-way valve 72 takes place counter to the actuating force of the spring element 74, and therefore stable pressure conditions arise at the valve.

(24) The actuating force can be changed via an electrically activatable third actuation device 76, and therefore an individual raising of the load-indicating pressure is possible, which takes into account the specific requirements of a particular attachment model.

(25) In addition, an enable valve designed as a further 2/2-way valve 78 is connected in series with the 2/2-way valve 72, wherein the further 2/2-way valve 78 is pilot-actuated via the externally prevailing load-indicating pressure in such a manner that the further 2/2-way valve takes up an open position when a predetermined pressure threshold value is exceeded. The further 2/2-way valve 78 ensures that the increased load-indicating pressure generated via the booster valve, i.e. the 2/2-way valve 72, is transmitted exclusively internally to the hydraulic supply 10 whenever a corresponding external supply requirement (attachment-side) prevails at the load-indicating line 26. The pressure threshold value arises here from the restoring force of a further spring element 80 which is dimensioned such that the further 2/2-way valve 78 reliably takes up its closed position in the unactuated state. The pressure threshold value arising to this extent is typically of the order of magnitude of 2 to 4 bar. For example, the further 2/2-way valve 78 is connected upstream of the 2/2-way valve 72, but it may also be connected downstream of the 2/2-way valve 72.

(26) Optionally, an orifice 84 for relieving the load-indicating line 26 of load in the direction of the hydraulic reservoir 28 is arranged on the load-indicating line 26 next to a filtering element 82, which is arranged directly downstream of the load-indicating port LS and prevents an undesired admission of contamination in the direction of the pilot-actuated 2/2-way valves 72, 78.

(27) The electrical activation of the respective actuation devices 46, 68, 76 for a certain attachment model, the activation being required for eliminating possible mismatches between the hydraulic supply 10 and attachment-side hydraulic system 16, takes place via a microprocessor-controlled control unit 86 (e.g., a controller including a processor and memory), with the relevant attachment model being selected via a user interface 88 communicating with the control unit 86.

(28) Proceeding from the illustrations in FIG. 1 and FIG. 2, the second actuation device 68 acts mechanically directly on the respective spring element 58, 66 to influence the restoring force. In a departure therefrom, it may also be provided, however, that a counterforce opposing the restoring force can be generated at the pressure-limiting valve 56 or at the pressure-reducing valve 64 via the second actuation device 68, with there not being a direct intervention in the spring element 58, 66. The same applies to the third actuation device 76 and to the spring element 74 associated therewith to this extent.

(29) The terminology used herein is for the purpose of describing example embodiments or implementations and is not intended to be limiting of the disclosure. As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the any use of the terms has, includes, comprises, or the like, in this specification, identifies the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

(30) Those having ordinary skill in the art will recognize that terms such as above, below, upward, downward, top, bottom, etc., are used descriptively for the figures, and do not represent limitations on the scope of the present disclosure, as defined by the appended claims. Furthermore, the teachings may be described herein in terms of functional and/or logical block components or various processing steps, which may include any number of hardware, software, and/or firmware components configured to perform the specified functions.

(31) Terms of degree, such as generally, substantially, or approximately are understood by those having ordinary skill in the art to refer to reasonable ranges outside of a given value or orientation, for example, general tolerances or positional relationships associated with manufacturing, assembly, and use of the described embodiments or implementations.

(32) As used herein, e.g., is utilized to non-exhaustively list examples and carries the same meaning as alternative illustrative phrases such as including, including, but not limited to, and including without limitation. Unless otherwise limited or modified, lists with elements that are separated by conjunctive terms (e.g., and) and that are also preceded by the phrase one or more of or at least one of indicate configurations or arrangements that potentially include individual elements of the list, or any combination thereof. For example, at least one of A, B, and C or one or more of A, B, and C indicates the possibilities of only A, only B, only C, or any combination of two or more of A, B, and C (e.g., A and B; B and C; A and C; or A, B, and C).

(33) While the above describes example embodiments or implementations of the present disclosure, these descriptions should not be viewed in a restrictive or limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the appended claims.