Hitachi, Ltd.

Hitachi Automotive Engineering Co., Ltd.

Other

Hitachi Car Engineering Co., Ltd.

Masuo Akamatsu

Izumi Watanabe

Hiroshi Yoneda

Shinya Igarashi

Kaoru Uchiyama

Masayoshi Suzuki

Tadashi Isono

Hiroatsu Tokuda

Chihiro Kobayashi

Takayuki Itsuji

Ryo Ando

In a heating resistor type air flow meter, a temperature characteristic of an air flow rate signal whose output value varies with temperature of the air flow meter circuitry is compensated by the temperature characteristic compensation circuit. The compensation circuit produces a temperature characteristic signal for compensation which changes in response to changes in an ambient temperature, and converts this signal into a predetermined proportional signal. The predetermined proportional signal is added to the air flow rate signal and such an addition result signal is input to the output control circuit and the temperature characteristic of the air flow rate signal is compensated. The resistors for proportional adjustment are external to and connected through a terminal to the IC of the air flow meter.

Heating resistor type air flow meter

An air meter is provided which enables the improvement of accuracy of internal reference voltages with few IC terminals. A band gap reference power supply circuitsupplies an internal reference voltage to a characteristic adjusting circuitand an internal reference voltage VINT to a multiplier circuitthe band gap reference power supply circuitcomprises a temperature current generating circuitfor generating a current proportional to a temperature, a current mirror circuit for duplicating the current of the temperature current generating circuita reference voltage generating circuitthrough which the current duplicated by the current mirror circuitis caused to be flowed to generate the internal reference voltage ES, and a reference voltage generating circuitthrough which the current duplicated by the current mirror circuitis caused to be flowed to generate the internal reference voltage VINT.

Air meter

A heating resistor type air flow rate measuring apparatus is provided with a couple of heating resistors placed at the positions where those resistors may each interfere thermally with respect to an air flow, and a couple of driving circuits for driving those heating resistors. The air flow rate signal is obtained by calculating the difference between the output signals of a couple of heating resistors in terms of heat radiation rate effected by an air flow, and adding the difference value onto the output signal of one of heating resistors.

Heating resistor type air flow rate measuring apparatus

An air meter is provided which enables the improvement of accuracy of internal reference voltages with few IC terminals. A band gap reference power supply circuit supplies an internal reference voltage to a characteristic adjusting circuit and an internal reference voltage VINT to a multiplier circuit . the band gap reference power supply circuit comprises a temperature current generating circuit for generating a current proportional to a temperature, a current mirror circuit for duplicating the current of the temperature current generating circuit , a reference voltage generating circuit through which the current duplicated by the current mirror circuit is caused to be flowed to generate the internal reference voltage ES, and a reference voltage generating circuit through which the current duplicated by the current mirror circuit is caused to be flowed to generate the internal reference voltage VINT.

A heating resistor type air flow rate measuring apparatus is provided with a couple of heating resistors placed at the positions where those resistors may each interfere thermally with respect to an air flow, and a couple of driving circuits for driving those heating resistors. The air flow rate signal is obtained by calculating the difference between the output signals of a couple of heating resistors in terms of heat radiation rate effected by an air flow, and adding the difference value onto the output signal of one of the heating resistors.

In a ratiometric output type air flow meter with a heat generating resistor, a ratiometric circuit is provided with a divider circuit which is constituted by invariable resistors and divides an external reference voltage Vref and a multiplier circuit. The invariable resistor is grounded, via the invariable resistor. To one of input terminals of the multiplier circuit an output signal V of an operational amplifier is inputted, to the other input terminal of the multiplier circuit voltage Vex divided by the invariable resistors is inputted, and the output signal Vout of the multiplier circuit is outputted to an engine control unit. A correction use resistor is connected at the junction of the invariable resistor and a current detection resistor, and is grounded via a ground wiring resistance. Thus the voltage drop Vg caused by the ground wiring is compensated by the correction use resistor, and the voltage (Vex&minus;Vg) representing the input to the multiplier circuit is kept constant regardless to the magnitude of a heating current flowing through the heat generating resistor. Thereby, a ratiometric output and heat generating resistor type air flow meter which permits a highly accurate air flow rate measurement is realized without being affected by variation due to the heating current flowing through the heat generating resistor.

Air flow meter with heat generating resistor

A heating resistor type air flow-meter has a ratio-meter circuit comprising a proportional circuit for outputting a signal V.sub.out proportional to an input voltage V.sub.in a multiplying circuit for outputting a multiplied signal V.sub.m proportional to a product of a voltage difference VD between an internal reference voltage VINT and an external reference voltage VREF and the voltage signal V.sub.in and an adding circuit for adding the output signal V.sub.p of the proportional circuit and the output signal V.sub.m of the multiplying circuit.

Heating resistor type air flow-meter of ratio-metric output type and

A heat type air flow meter with improved resistance to radio wave interference by restraining a high frequency noise from a resistor and the supporting materials thereof provided in air passage. At least one high frequency band cut-off filter having a capacitor and a inductor is provided between, on one hand, a heating resistor and a heat sensitive resistor and, on the other hand, a temperature control circuit, and an intermediate connecting point of one end of the capacitor connected with one end of the inductor is also connected to both resistors. Thereby, as the resistivity to the radio wave interference is effectively improved cost reduction and compactness of the flow meter can be achieved.

Heat type air flow meter

A hot wire type air flowmeter has a drive circuit for controlling the temperature of a hot wire type resistor and for outputting indications of controlling states as electric signals, an output adjusting circuit for adjusting the electric signals output from the drive circuit, and a subtracter provided in the output adjusting circuit of the hot wire type air flowmeter. The electric signals output from a non-inverting amplifier in the drive circuit are input to one input terminal of the subtracter and a standard voltage supplied via a voltage follower are input to the other input terminal of the subtracter.

Hot wire type air flowmeter

The present specification discloses a hot wire air flow meter with high circuit stability. The hot wire type air flow meter comprises a hot wire located in an air flow path to be measured and to which current is supplied from the external, a circuit for detecting a value of current flowing through the hot wire, an amplifying circuit including an inverting input terminal, a non-inverting input terminal to which a value detected in the current detecting circuit is applied, and an output terminal to which an output of an air-flow function is applied, a feedback circuit for supplying a feedback output to any terminal except the non-inverting input terminal of the amplifying circuit and controlling the output of the amplifying circuit to keep the temperature of the hot wire stable according to the output of the amplifying circuit, and a circuit for compensating for a phase of an output of the amplifying circuit contained in the feedback circuit.

Hot wire air flow meter

A hot wire type air flow meter employing a hot wire temperature dependent resistor having a heat generating portion and a non-heat generating portion comprising a feedback control circuit controlling the hot wire temperature dependent resistor temperature constant which includes a phase shift circuit for inducing a sufficient phase delay in feedback signals thereby compensating a second stage delay in output signals of the air flow meter caused by the thermal inertia of the non-heat generating portion and enhancing response characteristic of the air flow meter.

Air flow meter with compensation of second stage delay of thermal inertia

In a drive processing circuit comprising a flow velocity measuring resistor and a temperature compensating resistor of a hot wire type air flow meter, a resistor is inserted between a connecting point of two resistors and an inverting input terminal of an operational amplifier. A condenser is inserted between an inverting input terminal of the amplifier and the non-inverting input terminal of the amplifier. A resistant value of the inserted resistor is set larger than a resistant value of the temperature compensating resistor. A low pass filter comprises the inserted resistor and the inserted condenser. The high frequency noises, which intrude through the temperature compensating resistor, are cut-off by the low pass filter.

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Hitachinaka, Japan

Masuo Akamatsu