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EP-4378726-B1 - HYBRID SYSTEM AND WORKING MACHINE INCLUDING HYBRID SYSTEM

EP4378726B1EP 4378726 B1EP4378726 B1EP 4378726B1EP-4378726-B1

Inventors

  • YAGYU, SUMIO
  • HIRASE, Yuji
  • OKAZAKI, KAZUTO
  • II, Tsunehiro

Dates

Publication Date
20260506
Application Date
20231127

Claims (12)

  1. A hybrid system (25) comprising: an engine (7); a generator (9) configured to be driven by the engine (7); an electric actuator (26) configured to be driven by electricity generated by the generator (9); a transmission mechanism (27) configured to transmit power from the engine (7); a hydraulic pump (17) configured to receive power from the engine (7) through the transmission mechanism (27) to deliver hydraulic fluid; and a hydraulic actuator (28) configured to be driven by hydraulic fluid delivered by the hydraulic pump (17), wherein the transmission mechanism (27) includes a first transmission path (39) configured to transmit power from the engine (7) to the hydraulic pump (17) when a rotational speed of the engine (7) is a first rotational speed (R1), and a second transmission path (40) configured to transmit power from the engine (7) to the hydraulic pump (17) at a speed change ratio at which a rotational speed is increased to a greater degree than at a speed change ratio of the first transmission path (39) when the rotational speed of the engine (7) is a second rotational speed (R2) that is lower than the first rotational speed (R1); and the hybrid system further comprises a mode switch (53) configured to receive an operation to select one of a plurality of modes, and a controller (48) configured to switch the rotational speed of the engine (7) to the first rotational speed (R1) or to the second rotational speed (R2) according to the operation received by the mode switch (53).
  2. The hybrid system (25) according to claim 1, wherein the speed change ratios of the first transmission path (39) and the second transmission path (40) are defined such that a rotational speed inputted from the first transmission path (39) into the hydraulic pump (17) when the rotational speed of the engine (7) is the first rotational speed (R1) is substantially equal to a rotational speed inputted from the second transmission path (40) into the hydraulic pump (17) when the rotational speed of the engine (7) is the second rotational speed (R2).
  3. The hybrid system (25) according to claim 1 or 2, wherein the speed change ratio of the second transmission path (40) is defined as a value obtained by dividing a product of the speed change ratio of the first transmission path (39) and the first rotational speed (R1) by the second rotational speed (R2).
  4. The hybrid system (25) according to any one of claims 1 to 3, wherein the transmission mechanism (27) includes a first clutch (46) provided in the first transmission path (39); and the first clutch (46) is operable to transmit power from the first transmission path (39) to the hydraulic pump (17) when a rotational speed inputted into the first clutch (46) is higher than a rotational speed inputted from the second transmission path (40) into the hydraulic pump (17), and interrupt transmission of power from the first transmission path (39) to the hydraulic pump (17) when the rotational speed inputted into the first clutch (46) is lower than or equal to the rotational speed inputted from the second transmission path (40) into the hydraulic pump (17).
  5. The hybrid system (25) according to claim 4, wherein the transmission mechanism (27) includes a second clutch (47) provided in the second transmission path (40); and the second clutch (47) is operable to transmit power when the rotational speed of the engine (7) is the second rotational speed (R2), and not transmit power when the rotational speed of the engine (7) is other than the second rotational speed (R2).
  6. The hybrid system (25) according to claim 4 or 5, wherein the transmission mechanism (27) further includes: a first shaft (44); and a third transmission path (41) configured to transmit power from the engine (7) to the generator (9); wherein the third transmission path (41) includes: a transmission assembly (33) configured to transmit power from an output shaft (7a) of the engine (7) to an input shaft (9a) of the generator (9), the transmission assembly (33) being connected to the output shaft (7a); and a transmission shaft (52) configured to transmit power from the output shaft (7a) to the first transmission path (39) and the second transmission path (40), the transmission shaft (52) being connected to the output shaft (7a); wherein the first shaft (44) transmits power to the hydraulic pump (17), and wherein the first clutch (46) is provided on the first shaft (44) provided in front of the transmission shaft (52) to be aligned coaxially with the transmission shaft (52).
  7. The hybrid system (25) according to claim 6, wherein the input shaft (9a) is hollow, and the transmission shaft (52) extends through an interior of the input shaft (9a).
  8. The hybrid system (25) according to claim 4 or 5, wherein the transmission mechanism (27) includes: a first shaft (44); and a third transmission path (41) configured to transmit power from the engine (7) to the generator (9); wherein the third transmission path (41) includes: a transmission assembly (33) configured to transmit power from an output shaft (7a) of the engine (7) to an input shaft (9a) of the generator (9), the transmission assembly (33) being connected to the output shaft (7a); and a transmission shaft (52) configured to transmit power from the output shaft (7a) to the first transmission path (39) and the second transmission path (40), the transmission shaft (52) being connected to the output shaft (7a); wherein the first shaft (44) transmits power to the hydraulic pump (17), and wherein the first clutch (46) is provided on a fifth shaft (58) that is provided forward of the transmission shaft (52) but at a position offset radially outward from the transmission shaft (52).
  9. The hybrid system (25) according to claim 8, wherein the transmission shaft (52) extends in parallel to the input shaft (9a).
  10. The hybrid system (25) according to any one of claims 6 to 9, wherein the transmission assembly (33) is operable to transmit power received from the output shaft (7a) while increasing a rotational speed and transmit the power to the input shaft (9a).
  11. The hybrid system (25) according to any one of claims 1 to 10, further comprising an alternator (54) configured to generate electricity using power transmitted to the generator (9).
  12. A working machine (1) comprising: the hybrid system (25) according to any one of claims 1 to 11; a machine body (2); a traveling device (4) configured to be driven by the electric actuator (26) and configured to support the machine body (2) such that the machine body (2) is allowed to travel; and a working device (3) configured to be driven by the hydraulic actuator (28).

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a hybrid system and a working machine including a hybrid system. Description of the Related Art A working machine includes two types of hydraulic systems, i.e., a drive hydraulic system for driving tires or crawlers and an auxiliary hydraulic system for an arm, a bucket, an implement, and/or the like. However, the use of hydraulic pressure for driving tires or crawlers is generally considered to be inefficient. Therefore, in order to achieve high efficiency when driving working machines, hybrid working machines which operate partially or entirely on electricity are increasingly used. In the case of an automobile, as disclosed in Japanese Unexamined Patent Application Publication No. 2020-183164 (Patent Literature 1), an oil pump is used to cool a series hybrid generator or motor. Therefore, studies have been conducted to achieve sufficient flow rate and efficiency of the oil pump (hydraulic pump). US 2022/105793 A1 and DE 10 2021 109279 A1 each disclose a hybrid system comprising: an engine; a generator configured to be driven by the engine; an electric actuator (26) configured to be driven by electricity generated by the generator; a transmission mechanism configured to transmit power from the engine; a hydraulic pump configured to receive power from the engine through the transmission mechanism to deliver hydraulic fluid; and a hydraulic actuator configured to be driven by hydraulic fluid delivered by the hydraulic pump. Anonymous: "Choosing your PTO percentage: How fast is fast enough?", 26 August 2019 (2019-08-26), XP093146398, discloses a power take-off (PTO) in which a power outputted from an engine of a truck is used for driving a hydraulic pump, and mentions how to select the PTO based on a desired displacement of the hydraulic pump and the rotation speed of the engine. SUMMARY OF THE INVENTION In a series hybrid vehicle in which an engine, a generator, and a hydraulic pump are connected in series, power generated by the engine is directly transmitted to the generator and the hydraulic pump, and the electricity generation by the generator and driving of the hydraulic pump are performed concurrently. However, although the rotational speed of the engine may be changed in accordance with the output of the generator to further save energy on the hybrid vehicle, when the rotational speed of the engine is reduced, the reduced rotational speed of the engine may be appropriate for the output of the generator but may be below the rotational speed optimal for the operation of the hydraulic pump. One or more embodiments of the present invention were made in view of the above problem, and an object thereof is to provide a hybrid system capable of maintaining the driving of a hydraulic pump regardless of the rotational speed of an engine, and provide a working machine including a hybrid system. Technical solutions provided by one or more embodiments of the present invention to attain the above object include the following feature(s). A hybrid system according to an aspect of the present invention includes an engine, a generator to be driven by the engine, an electric actuator to be driven by electricity generated by the generator, a transmission mechanism to transmit power from the engine, a hydraulic pump to receive power from the engine through the transmission mechanism to deliver hydraulic fluid, and a hydraulic actuator to be driven by hydraulic fluid delivered by the hydraulic pump, wherein the transmission mechanism includes a first transmission path to transmit power from the engine to the hydraulic pump when a rotational speed of the engine is a first rotational speed, and a second transmission path to transmit power from the engine to the hydraulic pump at a speed change ratio at which a rotational speed is increased to a greater degree than at a speed change ratio of the first transmission path when the rotational speed of the engine is a second rotational speed that is lower than the first rotational speed, and wherein the hybrid system further comprises a mode switch to receive an operation to select one of a plurality of modes, and a controller to switch the rotational speed of the engine to the first rotational speed or to the second rotational speed according to the operation received by the mode switch. The speed change ratios of the first transmission path and the second transmission path may be defined such that a rotational speed inputted from the first transmission path into the hydraulic pump when the rotational speed of the engine is the first rotational speed is substantially equal to a rotational speed inputted from the second transmission path into the hydraulic pump when the rotational speed of the engine is the second rotational speed. The speed change ratio of the second transmission path may be defined as a value obtained by dividing a product of the speed change ratio of the first transmission path