Hitachi Koki Co., Ltd.

Kenrou Ishimaru

Nobuhiro Takano

Hidekazu Harada

Takao Aradachi

Takeshi Takeda

Toshio Mizoguchi

Yoshikazu Kawano

Tomoyuki Kawahara

Hiromi Ozawa

Hiroyuki Saitou

Eisaku Oka

Kazuhiko Funabashi

Shigeru Shinohara

Yukihiro Shima

Yoshio Iimura

Shigeru Moriyama

A digital miter saw for cutting a workpiece includes a base, a member supported on the base and moveable relative to the base, and a cutting member moveable with the member. A detector is provided for detecting at least one of a miter angle and a bevel angle between the cutting member and the workpiece, and for outputting a signal indicative of the at least one detected angle, and a digital controller is provided which has an interface operable to receive the signal.

Miter saw for displaying angle of cutter blade cutting workpiece

A DC power source unit supplies a DC voltage to a power tool through an adapter when a power switch of the tool is turned ON and also charges a battery pack used as an alternative power source of the tool when the power tool is not operated. In order to prevent a rush current from flowing in a switch interposed between a switching power source circuit and the battery pack when charging the battery pack is commenced, the switch is rendered OFF when the output voltage from the switching power source is greater than the battery voltage. Charging the battery is started upon once lowering the output of the switching power source to a level lower than the battery voltage.

DC power source unit with battery charging function

A DC power source unit supplies a DC voltage to a power tool through an adapter when a power switch of the tool is turned ON and also charges a battery pack used as an alternative power source of the tool when the power tool is not operated. A minimum battery temperature gradient amongst battery temperature gradients ever computed is used to determine whether the battery pack has cooling effect when forcibly cooled by a cooling fan or whether the battery pack has reached a full charge condition. When charging the battery pack is interrupted due to operation of the power tool, computing the battery temperature gradient is halted for some time or determination of the battery pack's full charge condition is not performed for some time in order to prevent the minimum battery temperature from being updated during interruption of charging of the battery pack.

A battery charger for charging a battery pack having a battery, a temperature sensor for sensing a temperature of the battery, and a battery terminal. The battery charger includes a charger terminal to which the battery terminal is connected when the battery is charged, a charge current generating circuit that generates a charge current for charging the battery, a battery temperature detector, and a controller. The battery temperature detector is configured to include a circuit, for example, to detect a temperature of the battery while cooperating with the temperature sensor and to output a temperature signal indicative of the temperature of the battery. The controller which is supplied with the temperature signal from the battery temperature detector, corrects the temperature signal, and provides a corrected temperature signal.

Battery charger capable of accurately detecting battery temperature for full charge determination

A miter saw for displaying angle of a cutter blade cutting the workpiece. The miter saw has a base mounting a workpiece thereon, a movable member movably supported to the base, and a cutting unit connected to the movable member for supporting the cutter blade. A positioning portion is associated with the movable member and provides a predetermined nominal position of the movable member with respect to the base. The predetermined nominal position includes a reference position and other positions labeled angle. A detector detects the position of the movable member with respect to the base. A processor sets an angle between the reference position and the predetermined nominal position as a displayed moving amount when the movable member is positioned at the predetermined nominal position. Otherwise, the processor computes the moving amount based on the output signal from the detector.

To provide a battery charger capable of fully charging both an active battery and an inactive battery, which have different charging characteristics near the peak level, a voltage across the battery is periodically sampled during charging the battery. A voltage change is obtained by subtracting a voltage that has been sampled previously from the newly sampled voltage. Determination of the fully charged condition of the battery is made when a voltage change falls below a critical value (S , S ) after identifying that the battery being charged is an active or inactive battery using another critical values (K , K or K &prime;, K &prime;). The critical values S and S and another critical values K and K (or K &prime; and K &prime;) are selectively referred to depending to the battery voltage change.

Battery charger capable of accurately determining fully charged condition regardless of batteries with different charge chracteristics

To provide inexpensive and economic battery chargers with excellent productivity, a control circuit board for the battery charger is produced so as to be usable in common for both the battery chargers with a cooling device and the battery chargers without a cooling device. In the control circuit board, a cooling device detection circuit is provided for detecting whether or not the cooling device is provided. An average charge current to be applied to a battery pack to be charged is controlled depending on whether or not the cooling device is provided. The average charge current is further controlled depending on the type of the battery pack, i.e., whether it is of a small rated capacity or of a large rated capacity, and on a rate of change in battery temperature at the time of start of charging.

Battery charger determining charging conditions depending upon whether a cooling device is provided

A charging circuit generates a charging current from an ac supply which is supplied to a secondary battery in a battery package through first terminals. A second terminal receives a temperature detection signal from a thermistor on the secondary battery. A value of the temperature detection signal is sampled every predetermined interval. A memory stores the sampled value. A difference between the sampled value and the value from the memory is obtained, as well as the temperature decrease value between the sampled value and the value stored, when it applies. An error signal is generated when the difference is higher than a predetermined value and the operator is alarmed and informed of the error. The difference may be obtained between the sampled value and the value one-cycle-previously-sampled value from the memory, between the sampled value and a minimum of the sampled values, or between the sampled value and a charging start value of the sampled value. The thermistor is supplied with a supply voltage through a switch and an error condition caused by leakage of the electrolyte from the battery is detected when the voltage at the second terminal is higher than the predetermined value, the charging current generation circuit is controlled to stop generating the charging current.

Battery charging apparatus with error detection

A microcomputer performs a total of 100 sampling actions during a 1 sec sampling period for obtaining a plurality of battery voltage data V. In each sampling period, a minimum value .upsilon.min and a maximum value .upsilon.max are stored in a RAM 53. A peak value VMAX, used for detecting a peak battery voltage in the charging operation, is renewed by a largest data among the sampled minimum values .upsilon.min. A differenc .DELTA.V between the peak value VMAX and the maximum value .upsilon.max is calculated the end of each sampling period. And, when the calculated difference .DELTA.V exceeds a predetermined value, a judgement is made that the battery is fully charged.

Battery charging operation and a detection of a fully charged condition

A battery charger having a battery charger converter, which converter consists of a battery voltage detector for detecting the voltage of a secondary battery and a differential amplifier disposed between the battery voltage detector and an A/D converter. This battery charger is capable of reliably detecting when any battery has become fully charged, including inactive batteries such as batteries that are still warm from recently being discharged and batteries that have been inactive for a long period of time.

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Hitachinaka, Japan

Kenrou Ishimaru