Patents by Inventor Toichi Hirata
Toichi Hirata has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 5168705Abstract: A flow control valve has a first variable restrictor to control a flow rate of a hydraulic fluid supplied from a hydraulic fluid supply line to a hydraulic actuator and a second variable restrictor to control a flow rate of the hydraulic fluid discharged from the hydraulic actuator to a hydraulic fluid return line. A pressure compensating valve holds constant a differential pressure across the first variable restrictor, and a recovery circuit having a recovery line has a check valve that allows flow of the hydraulic fluid only toward the supply line. The recovery circuit receives at least part of the hydraulic fluid discharged from the hydraulic actuator and returns it to the supply line at a portion between the pressure compensating valve and the first variable restrictor through the recovery line upon controlling of the discharged flow rate by the second variable restrictor to thereby recover the discharged hydraulic fluid.Type: GrantFiled: February 28, 1991Date of Patent: December 8, 1992Assignees: Hitachi Construction Machinery Co., Ltd., Kayaba Industry Co., Ltd.Inventors: Toichi Hirata, Hideaki Tanaka, Kazunori Nakamura, Hideshi Koiwai, Yoneaki Takahashi
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Patent number: 5161575Abstract: There is disclosed a direction selector valve having function of detecting load. The valve is used in a hydraulic system. A spool has two passage holes extending axially partially through the spool from both side ends. These two passage holes have their respective high-pressure holes. When the spool is in its neutral position, the high-pressure holes are closed off by spool hole walls between bridge ports and actuator ports. The two passage holes further include low-pressure holes which are in communication with tank ports via load check valves mounted in the passage holes, respectively. Guide holes are formed near the front end of one passage hole and in communication with a load-sensing port. A restriction portion is formed on the outer surface of the spool adjacently to the guide holes to control the flow from the load-sensing port to the tank ports. First guide holes and second guide holes which are close to each other are formed near the front end of the other passage hole.Type: GrantFiled: June 19, 1991Date of Patent: November 10, 1992Assignees: ZEXEL Corporation, Hitachi Construction Machinery Co., Ltd.Inventors: Rindo Morikawa, Kiyoshi Oyama, Toichi Hirata, Yusuke Kajita, Genroku Sugiyama
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Patent number: 5155996Abstract: A hydraulic drive system for a construction machine comprising a prime mover (1), a hydraulic pump (2) of variable displacement type driven by the prime mover, at least one hydraulic actuator (6) driven by a hydraulic fluid delivered from the hydraulic pump, control valves connected between the hydraulic pump and the actuator for controlling a flow rate of the hydraulic fluid supplied to the actuator dependent on the operation amount of control apparatus, pump control apparatus for controlling a displacement volume of the hydraulic pump dependent on the operation amount of the control apparatus such that the delivery rate of the hydraulic pump is increased with an increase in the operation amount, and prime mover control apparatus (29) for controlling a revolution speed of the prime mover.Type: GrantFiled: August 20, 1990Date of Patent: October 20, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Akira Tatsumi, Toichi Hirata, Masakazu Haga, Eiki Izumi
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Patent number: 5152140Abstract: A hydraulic drive system has a hydraulic pump (1), an actuator (2), a flow control valve (5) disposed between the hydraulic pump and the actuator, a pressure compensating valve (8; 8A; 8B) having a valve spool (23; 23A; 23B) that controls the differential pressure (Pz-PLS) across the flow control valve, and a pump delivery rate control device (9) for controlling a flow rate of the hydraulic fluid delivered from the hydraulic pump dependent on a differential pressure (Pd-PLS) between a pump pressure and a load pressure of the actuator.Type: GrantFiled: February 6, 1991Date of Patent: October 6, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Hideaki Tanaka, Genroku Sugiyama, Yusuke Kajita, Kazunori Nakamura
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Patent number: 5152143Abstract: A hydraulic drive system comprising a prime mover (21), a hydraulic pump (22) driven by the prime mover, a plurality of hydraulic actuators (23-28) driven by hydraulic fluid supplied from the hydraulic pump, a plurality of flow control valves (29-34) for controlling flow of the hydraulic fluid supplied to the actuators, and a plurality of pressure compensating valve (35-40) for controlling respective differential pressures across the respective flow control valves, in which each of the pressure compensating valves applies a control force (f-F.sub.c) in a valve opening direction for setting a target value of the differential pressure across the flow control valve. There are provided a first detector (60) for detecting the target rotational speed (N.sub.0) of the prime mover (21), and controllers (61, 62, 63) for controlling the control force on the basis of the target rotational speed detected by at least the first detector such that the control force (f-F.sub.Type: GrantFiled: December 21, 1989Date of Patent: October 6, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Yusuke Kajita, Toichi Hirata, Genroku Sugiyama
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Patent number: 5150574Abstract: A hydraulic drive system for a construction machine has a flow control valve (5) disposed between a hydraulic pump and an acutator, a pressure compensating valve for controlling a differential pressure across the flow control valve, and a pump delivery rate regulator for controlling a flow rate of the hydraulic fluid delivered from the hydraulic pump dependent on a differential pressure (Pd-PLS) between a pump pressure and a load pressure of the actuator. The pressure compensating valve has a valve body subjected to control forces. A first control force based on the differential pressure across the flow control valve to the valve body urges the valve body in the valve-closing direction. A second predetermined control force urges the valve body in the valve-operating direction; and a third control force based on the differential pressure (Pd-PLS) between the pump pressure and the load pressure of the actuator urges the valve body in the valve-opening direction.Type: GrantFiled: September 24, 1990Date of Patent: September 29, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Hideaki Tanaka, Genroku Sugiyama, Yusuke Kajita
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Patent number: 5146747Abstract: A valve apparatus (10; 10A) has at least one directional control valve (31; 31A) having a pair of variable restricting sections (43, 44) disposed between a supply passage (35) communicating with a hydraulic fluid supply source (11) and a pair of load passages (36, 37) communicating with an actuator (12). A pressure controller (32) or a pressure compensating valve (32A) is provided for holding a differential pressure across the variable restricting sections at a predetermined value. A detection line (57; 57A) is branched from a first passage (32; 86, 87) located between the pair of variable restricting sections and the pair of load passages for receiving a load pressure produced upon operation of the actuator. A check valve (59) or shuttle valve (90, 91) is provided for selecting a maximum load pressure and a control line (61, 62) introduces the selected maximum load pressure, as a control pressure, to the pressure controller or pressure compensating valve.Type: GrantFiled: December 18, 1990Date of Patent: September 15, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Genroku Sugiyama, Toichi Hirata
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Patent number: 5140815Abstract: A hydraulic actuator is driven by hydraulic fluid discharged from a hydraulic pump, for controlling driving of the actuator. A valve has a meter-in circuit for introducing the hydraulic fluid discharged from the hydraulic pump into the actuator. The valve also has a meter-out circuit for returning fluid from the actuator, into a tank. The meter-out circuit is provided with a main valve for controlling the return fluid from the actuator, and a pilot circuit including a variable restrictor. When the main valve is closed, the pilot circuit is closed, and when the main valve is open, its degree of opening varies depending upon an amount of restriction of the variable restrictor. A controller varies the amount of restriction of the variable restrictor valve in accordance with the driving pressure of the actuator.Type: GrantFiled: October 23, 1989Date of Patent: August 25, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Genroku Sugiyama, Toichi Hirata, Hideaki Tanaka, Kazumasa Yuasa, Yusaku Nozawa
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Patent number: 5134853Abstract: A hydraulic drive system for construction machines includes a hydraulic pump (1), a plurality of hydraulic actuators (2, 3) driven by a hydraulic fluid supplied from the hydraulic pump, a plurality of flow control valves (4, 5) for controlling flow rates of the hydraulic fluid supplied to the actuators, respectively, and a plurality of distribution compensating valves (6, 7) for controlling differential pressures across the flow control valves, respectively, the plurality of actuators including a first actuator (2) which undergoes a relatively large load pressure and a second actuator (3) which undergoes a smaller load pressure than that of the first actuator.Type: GrantFiled: November 16, 1989Date of Patent: August 4, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Genroku Sugiyama, Yusuke Kajita
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Patent number: 5101629Abstract: A hydraulic circuit system comprising a hydraulic-fluid supply source, at least one hydraulic actuator operated by hydraulic fluid from the hydraulic-fluid supply source, a flow control valve for controlling the flow of the hydraulic fluid to be supplied to the actuator and a pressure control element for maintaining the differential pressure across the flow control valve at a predetermined value.Type: GrantFiled: July 2, 1990Date of Patent: April 7, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Genroku Sugiyama, Toichi Hirata
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Patent number: 5085051Abstract: A hydraulic drive system has a variable displacement type pump, at least one hydraulic actuator driven by hydraulic fluid and a directional control valve for controlling a flow of the hydraulic fluid supplied to the actuator. The flow rate of the hydraulic fluid discharged from the hydraulic pump is controlled by a drive device that drives a displacement volume varying device of the hydraulic pump. A load-sensing control device controls the operation of the drive device and is responsive to a differential pressure between a discharge pressure of the hydraulic pump and a load pressure of the actuator to thereby hold the differential pressure at a setting value. The drive system further has an instruction device that instructs a change in the differential pressure between the discharge pressure of the hydraulic pump and the load pressure of the actuator. The instruction is received by a differential pressure setter capable of changing the setting value of the differential pressure.Type: GrantFiled: June 28, 1989Date of Patent: February 4, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventor: Toichi Hirata
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Patent number: 5083430Abstract: A hydraulic driving apparatus has at least one hydraulic pump, a plurality of hydraulic actuators driven by hydraulic fluid discharged from the hydraulic pump, a tank to which return fluid from the plurality of hydraulic actuators is discharged, and a flow control valve associated with each of the plurality of hydraulic actuators. The flow control valve has a first main variable restrictor for controlling flow rate of the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator, and a second main variable restrictor for controlling flow rate of the return fluid discharged from the hydraulic actuator to the tank. A pump control operative in response to the difference between the discharge pressure of the hydraulic pump and the maximum load pressure of the hydraulic actuators normally controls the discharge rate of the hydraulic pump so that the pump discharge pressure is raised more than the maximum load pressure by a predetermined value.Type: GrantFiled: November 13, 1989Date of Patent: January 28, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Hideaki Tanaka, Genroku Sugiyama, Yusaku Nozawa
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Patent number: 5079919Abstract: A hydraulic drive system for a crawler mounted vehicle has a hydraulic pump, a plurality of actuators including a pair of left and right travel motors and at least one other actuator that are driven by hydraulic fluid delivered from the hydraulic pump. The system further contains a plurality of flow control valves for controlling flows of the hydraulic fluid supplied to the respective actuators, and a plurality of distribution compensating valves for controlling differential pressures across the respective flow control valves, the plurality of distribution compensating valves each having drive parts to set a target value of the differential pressure across the associated flow control valve. The hydraulic drive system also has a speed selector for outputting a select signal to change operation speeds of the pair of travel motors, and a controller and a control pressure generator for controlling the drive parts of the distribution compensating valves associated with the pair of travel motors.Type: GrantFiled: August 28, 1990Date of Patent: January 14, 1992Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Kazunori Nakamura, Toichi Hirata
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Patent number: 5074194Abstract: In a hydraulic machine such as, for example, a hydraulic excavator equipped with hydraulic actuators, a hydraulic driving method and a hydraulic driving apparatus enable all the hydraulic actuators to be operated according to normal operational-speed characteristics (first mode). The method and the apparatus alter the operational-speed characteristics of at least one of the hydraulic actuators, according to other characteristics (second mode), in accordance with working contents. The actuators altered in this manner can be operated according to the operational-speed characteristics of the second mode, without exerting an influence upon the operational-speed characteristics of the remaining hydraulic actuators.Type: GrantFiled: October 27, 1989Date of Patent: December 24, 1991Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Kuniaki Yoshida, Hideaki Tanaka, Genroku Sugiyama, Masakazu Haga
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Patent number: 5062350Abstract: A hydraulic drive system for a civil engineering and construction machine of the present invention comprises a hydraulic pump (11, 11A), a plurality of actuators (4-6) driven by a hydraulic fluid supplied from the hydraulic pump and including an arm cylinder (5) and a boom cylinder (4), a plurality of flow control valves (12, 14, 16) for controlling flows of the hydraulic fluid supplied to the respective actuators and including an arm directional control valve (14) and a boom directional control valve (12) and a plurality of distribution compensating valves (13, 15, 17; 13A, 15A, 17A) for controlling differential pressures across the respective flow control valves, the distribution compensating valves each having a first device (13d,15d, 17d; 13e, 13f, 15e, 15f, 17e, 17f) to set a target value of the differential pressure across the associated flow control valve.Type: GrantFiled: July 12, 1990Date of Patent: November 5, 1991Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Hideaki Tanaka, Toichi Hirata, Genroku Sugiyama, Masakazu Haga, Yusuke Kajita
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Patent number: 5056312Abstract: A hydraulic system for a construction machine comprising plural hydraulic actuators (23-28) driven by fluid supplied from a pump (22), first and second flow control valves (29-34) for controlling flows of fluid supplied to the first and second actuators, and first and second distribution compensating valves (35-40) for controlling first differential pressure (.DELTA.P v1-.DELTA.P v6) produced between inlets and outlets of the first and second flow control valves. The first and second distribution compensating valves have respective drives (45-50, 35c-40c) for applying control forces (Fc1-Fc2) in accordance with the second differential pressure to the associated distribution compensating valves, to thereby set target values of the first differential pressures. The hydraulic system includes first means (59) for detecting the second differential pressure (.DELTA.Type: GrantFiled: November 22, 1989Date of Patent: October 15, 1991Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Genroku Sugiyama, Yusuke Kajita, Yukio Aoyagi, Tomohiko Yasudi, Gen Yasuda, Hiroshi Watanabe, Eiki Izumi, Yasuo Tanaka, Hiroshi Onoue, Shigetaka Nakamura
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Patent number: 5048296Abstract: A working machine such as a hydraulic excavator is provided with a working apparatus including a boom pivotally mounted on the body of the working apparatus and a boom-cylinder hydraulic system for the working apparatus. The hydraulic system includes an actuator for moving the boom up and down and a directional selecting valve. The directional selecting valve is arranged to effect selective switching of the feed of a pressurized working fluid to and the discharge of the working fluid from with respect to the rod-side and the bottom-side hydraulic chamber. The hydraulic system further includes a device for relieving the pressure of the bottom-side hydraulic chamber of the actuator. This relieving device is connected to the bottom-side hydraulic chamber of the actuator via a hydraulic circuit. When the pressure in the bottom-side hydraulic chamber changes from rise to fall, the pressure is released to a low-pressure side of the hydraulic circuit, thereby suppressing oscillation of the boom.Type: GrantFiled: January 9, 1990Date of Patent: September 17, 1991Assignee: Hitachi Construction Co., Ltd.Inventors: Kazuhiro Sunamura, Osamu Tomikawa, Toichi Hirata
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Patent number: 5005358Abstract: A hydraulic drive system for a crawler-mounted construction vehicle includes: a hydraulic pump (1); a plurality of hydraulic actuators including traveling hydraulic motors (2, 3) driven by the hydraulic pump; a plurality of flow control valve means including first and second flow control valve means (15, 16; 35, 36) for respectively controlling the flow rates of the hydraulic fluid supplied from the pump to motors; pump controlling means (11) for effecting control during the driving of the motors in such a manner that the discharge pressure of the pump becomes higher by a fixed value than the higher one of load pressures of the motors; and first and second pressure balance valve means (17, 18; 37, 38) for respectively controlling the rates of flow through the flow control valve means during the driving of the motors in such a manner that the load pressures of the motors do not affect the rates of flow through the first and second flow control valve means.Type: GrantFiled: May 10, 1989Date of Patent: April 9, 1991Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Toichi Hirata, Hideaki Tanaka, Genroku Sugiyama, Yusuke Kajita
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Patent number: 4967557Abstract: Control system for a load-sensing hydraulic drive circuit comprising; at least one hydraulic pump; hydraulic actuators driven by the hydraulic pump; and a pressure compensated flow control valve between the pump and each of the actuators, for controlling a flow rate of fluid to each actuator in response to a control signal. The control system has first detection means for detecting a differential pressure between the pump delivery pressure and the maximum load pressure; second detection means for detecting the pump delivery pressure; first means for calculating a differential pressure target pump delivery amount Q.DELTA.p to hold the differential pressure constant; second means for calculating an input limiting target pump delivery amount QT based on at least a pressure signal from the second detection means and an input limiting pump function; third means for selecting one of the differential pressure target delivery amount Q.DELTA.Type: GrantFiled: January 26, 1989Date of Patent: November 6, 1990Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Eiki Izumi, Yasuo Tanaka, Hiroshi Watanabe, Kuniaki Yoshida, Toichi Hirata
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Patent number: 4955344Abstract: A controller having an up/down switch for changing the rotational speed of a prime mover such as an engine, an actuator such as an electric motor for driving a governor on the basis of the operation of the up/down switch so as to control the rotational speed of the prime mover. A target speed is calculated on the basis of the operation of the up/down switch, and the prime mover speed is controlled by using the calculated value. Another switch is provided to immediately shift the prime mover speed to a speed previously set as desired. This shift switch is used to control the prime mover so that the prime mover rotates at the set speed, and this speed is adjusted by operating the up/down switch.Type: GrantFiled: July 3, 1989Date of Patent: September 11, 1990Assignee: Hitachi Construction Machinery Co., Ltd.Inventors: Akira Tatsumi, Toichi Hirata, Masaki Egashira, Osamu Tomikawa, Hiroshi Watanabe