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NO-349291-B9 -

NO349291B9NO 349291 B9NO349291 B9NO 349291B9NO-349291-B9

Dates

Publication Date
20260202
Application Date
20200617
Priority Date
20190617

Claims (7)

  1. 1. 349291 20 PATENT CLAIMS 1. Construction machine (1) comprising: a frame on a chassis for moving the machine; <5>a boom operable to move relative to the frame; and at least one closed hydraulic circuit that can be operated individually and that includes: a volume-neutral cylinder mechanically connected to the excavator boom, the volume-neutral cylinder comprising: <10>a piston member (300); a cylinder portion (200); one or more pressure chambers (TR) arranged to receive a fluid for applying a pressure against one or more pressure surfaces (TF) for displacing the piston member (300) in a first stroke direction (A); <15>characterized by: the volume-neutral cylinder further comprises: at least two return pressure spaces (RTR1, RTR2, RTR3) arranged for fluid communication therebetween and for receiving a fluid for applying a pressure against at least two return pressure surfaces (RTF1, RTF2, RTF3) for displacement of the stem- <20 >the pile part (300) in a second return stroke direction (B); wherein the pressure surface(s) (TF) and the return pressure surfaces (RTF1, RTF2, RTF3) are configured for volume neutral or nearly volume neutral operation of the cylinder; and the smallest one closed circuit further comprises: <25>a fluid pump hydraulically connected to the cylinder, the fluid pump arranged to generate hydraulic pressure and fluid flow in the closed circuit between the pump and the volume-neutral cylinder for actuating the cylinder and thereby the boom. 349291 21
  2. 2. Construction machine as set forth in claim 1, wherein the pump is driven by an electric motor connected to a battery, wherein the speed and direction of rotation of the electric motor and the fluid pump are controllable from a PLC control unit for speed and direction of rotation.
  3. <5 >3. Construction machine as claimed in claim 1 or 2, configured for power transmission from battery to cylinder.
  4. 4. A construction machine as claimed in any preceding claim, wherein the fluid pump is connected to an electric motor and the closed circuit has a first mode and a second mode. <10> mode; wherein in said first mode, the electric motor is used as a motor to drive the pump for actuating the cylinder comprising displacing the piston member in the first or second stroke direction, and where in said second mode, the electric motor is used as a generator to generate <15 >re power to a battery on the construction machine where the load on the cylinder during lowering of the load drives the pump to generate or regenerate energy.
  5. 5. Construction machine as claimed in any preceding claim, battery powered. <20 >
  6. 6. A construction machine as claimed in any preceding claim, further comprising a plurality of volume-neutral hydraulic cylinders and a corresponding plurality of closed hydraulic circuits, each closed hydraulic circuit comprising one volume-neutral hydraulic cylinder of said plurality of volume-neutral hydraulic cylinders, and a pump directly connected hydraulically to the one volume-neutral cylinder, the fluid pump being adapted to generate <25 >reduces hydraulic pressure and fluid flow in the closed circuit between the pump and the volume-neutral cylinder for activation of the cylinder and thereby the boom.
  7. 7. Excavator (90) comprising: an electrohydraulic system; 349291 22 a plurality of volume-neutral cylinders end-mounted on the excavator, comprising a boom cylinder (8) for operating an excavator boom (5); a stick cylinder (6) for operating an excavator stick (9); and a bucket cylinder (7) for operating an excavator bucket (15); a cab (4) containing operating levers (25) with control unit (24) for <5>operating cylinder functions for the cylinders (6, 7, 8); a transport device (11) for moving the excavator (90); a frame structure (35) on top of the transport device (11), the frame structure being rotatable relative to the transport device about a vertical axis (36); batteries (10); <10 >wherein the electrohydraulic system (99) comprises: a swing motor (3) which provides rotation of the frame structure about the vertical axis (36); electrohydraulic units, each unit comprising an electric motor (16), a fluid pump (18) and a frequency converter (13); and wherein the cylinder (6, 7, 8) is connected to the fluid pump (18) in a closed hydraulic circuit; <15>wherein each of said volume-neutral cylinders comprises: a piston member (300); a cylinder portion (200); one or more pressure chambers (TR) arranged to receive a fluid to apply a pressure against one or more pressure surfaces (TF) for displacing the piston member (300) in a <20 >first stroke direction (A); characterized by: each of said volume-neutral cylinders further comprising: at least two return pressure chambers (RTR1, RTR2, RTR3) arranged for fluid communication therebetween and for receiving a fluid to apply a pressure to at least <25>two return pressure surfaces (RTF1, RTF2, RTF3) for displacing the piston part (300) in a second return stroke direction (B); wherein the pressure surface(s) (TF) and the return pressure surfaces (RTF1, RTF2, RTF3) are configured for volume neutral or nearly volume neutral operation of the cylinder; wherein each of the cylinders (6, 7, 8) is connected to and operated by its own fluid pump (18) <30>driven by an electric motor (16) whose speed is regulated by a frequency converter (13) connected to the battery (10); 349291 23 wherein the electric motor (16) drives the fluid pump (18) which generates a hydraulic pressure and fluid flow for actuating the cylinder (6, 7, 8); where the frequency converter (13) regulates the speed and direction of rotation of the electric motor (16), so that the stroke direction of the cylinder (6, 7, 8) is regulated directly from the electric motor <5 >tor (16), without the use of directional valves; where the hydraulic system is configured to operate so that: when the digging boom, stick, or bucket is operated to be raised, a fluid flow and a fluid pressure are supplied to said pressure chamber (TR) in the cylinder, and the piston member (300) is displaced out of the cylinder housing (200); and <10>When the excavator boom, stick, or bucket is lowered, energy is regenerated by fluid flowing through the pump (18) so that it functions as a motor, and the electric motor (16) functions as a generator that generates energy for the battery (10) through the frequency converter (13).

Description

[0001] 349291 [0003] 1 [0005] CONSTRUCTION MACHINERY AND EXCAVATOR [0007] The invention relates to a construction machine and an excavator, which in various embodiments use a volume-neutral cylinder. [0009] Background [0011] <5>In construction machinery today, hydraulic systems are used to transfer forces to work operations to be performed. This can include, for example, excavators and loaders where hydraulic cylinders are used to convert fluid pressure and fluid flow into linear movements with great force. [0013] A hydraulic system for a construction machine includes one or more hydraulic pumps that [0014] <10 >typically driven by an internal combustion engine, and a plurality of hydraulic functions, for example cylinders and motors. Directional valves ensure that the desired amount of oil is supplied to the various hydraulic functions. Throttling and pressure drop in the valves can cause a large energy loss in the form of heat which is then typically cooled by coolers in the oil circuit. Today's hydraulic systems are not optimized with regard to energy consumption, but this has not been addressed in the [0015] <15>sjen because access to energy from internal combustion engines has been cheap. [0017] The construction industry, and especially construction machinery that emits a lot of CO2, is now facing demands for emission reductions of greenhouse gases and increased requirements for HSE. [0019] One solution to reduce emissions is to use batteries as an energy source. Batteries are less energy-dense than internal combustion engines. This means, for example, that a battery-powered [0020] <20> construction machine will require significantly longer time for energy supply than a similar machine. [0021] 349291 [0023] 2 [0025] a piling machine with a combustion engine, which provides reduced operating time for a battery-powered excavator. [0027] Another solution is to regenerate energy from the machines' hydraulic system, for example by utilizing the oil pressure in the cylinders of a boom on an excavator. The patent specification [0028] <5>NO317269 describes an excavator with a separate hydraulic boom cylinder arranged to generate a counterforce and an additional hydraulic pressure that can be used to reduce the power and energy requirement when lifting the excavator boom. [0030] Patent document EP3150861 describes an excavator in which the directional valves for the boom cylinder, the stick cylinder and the bucket cylinder are replaced with a plurality of closed and [0031] <10> independent oil circuits. Each circuit comprises a double-acting cylinder, a motor and an oil pump. Because the cylinders have different pressure volumes and return volumes, each oil motor is connected to an oil tank so that excess oil can be drained from the return volume when the cylinder is moved in a pressure direction, and from the tank to the return volume when the cylinder is moved in a return direction. [0033] <15 >Patent document JP2005344776A also describes an excavator with closed hydraulic circuits for the excavator's boom cylinder, stick cylinder and bucket cylinder. Furthermore, a volume-neutral cylinder is described so that the amount of oil in each circuit can be kept constant. The volume-neutral cylinder has a continuous piston rod, where one free end of the piston rod is housed by an additional cylinder space, which gives the cylinder an ex- [0034] <20>tra installation length corresponding to the cylinder stroke length. [0036] The invention aims to remedy or reduce at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art. [0038] The object is achieved by the features set forth in the description below and in the following patent claims. [0040] <25>In a first aspect, the invention relates to a construction machine as set forth in claim 1. The construction machine may have further features as set forth in one or more of claims 1 to 6. [0042] In a second aspect, the invention relates to an excavator as set forth in claim 7. [0043] 349291 [0045] 3 [0047] General description [0049] Described according to a first example is a cylinder comprising: a piston portion; a cylinder portion arranged for movement axially relative to the piston portion; one or more pressure chambers arranged to receive a fluid for applying a pressure against one or more pressure surfaces for displacement. [0050] <5 >ning of the piston part in a first stroke direction; and one or more return pressure chambers arranged to receive a fluid for applying a pressure against one or more return pressure surfaces for displacing the piston part in a second return stroke direction; the cylinder part and/or the piston part comprises a tube portion that encloses one or at least one of said pressure chambers and/or pressure surface(s) in a radially inner region of the cylinder; and the cylinder part and/or the piston part further comprises [0051] <10>comprises one or at least one of said return pressure spaces a