Back to results
US 2003/0192378 A1Published application
Air meter
AssigneeHitachi, Ltd.
InventorMasuo Akamatsu
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeHitachi, Ltd.
InventorMasuo Akamatsu
Estimating the term…
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 6 supplies an internal reference voltage to a characteristic adjusting circuit 4 and an internal reference voltage VINT to a multiplier circuit 5. the band gap reference power supply circuit 6 comprises a temperature current generating circuit 21 for generating a current proportional to a temperature, a current mirror circuit for duplicating the current of the temperature current generating circuit 21, a reference voltage generating circuit 23 through which the current duplicated by the current mirror circuit 22 is caused to be flowed to generate the internal reference voltage ES, and a reference voltage generating circuit 24 through which the current duplicated by the current mirror circuit 22 is caused to be flowed to generate the internal reference voltage VINT.
An air meter having a characteristic adjusting circuit for adjusting the characteristic of a flow rate signal detected by flow rate detecting means, by using a first internal reference voltage, and outputting the flow rate characteristic signal, a conversion circuit for converting the flow rate characteristic signal which this characteristic adjusting circuit outputs, to a ratio-metric output or a frequency output on the basis of a second internal reference voltage, and a reference power supply circuit for said first and second internal reference voltages, said internal reference power supply circuit comprising:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
By using thermal effects: circuits therefor, e.g. constant-current flow meters
Circuits therefor, e.g. constant-current flow meters: comprising means to store calibration data for flow signal calculation or correction
Measuring volume, volume flow, mass flow or liquid level
Term end not estimated
This invention relates to an air meter, particularly to an air meter for measuring air mass flow suitable for the use of engine control for an automobile.
As the prior art air meter, a ratio-metric output type air meter is known having an output characteristic adjusting circuit and a ratio-metric converting circuit, as shown in Japanese Patent Prepublication No. 148556/1998. Also, in a frequency output type air meter, a ratio-metric output type air meter is known having an output characteristic adjusting circuit and a voltage controlled oscillator circuit.
However, in both of the ratio-metric output type air meter and the frequency output type air meter, two circuits of the respective air meters have independent internal reference power supply circuits, and to assure their accuracy it is necessary that a resistor is connected to the external of a monolithic IC, and therefore, it is necessary that the IC has connection terminals of the number proportional to the number of the internal reference power supply circuit outputs.
FIG. 1 is a circuit diagram of an air meter according to a first embodiment of this invention;
FIG. 2 is a circuit diagram of an air meter according to a second embodiment of this invention; and
FIG. 3 is a circuit diagram of an air meter according to a third embodiment of this invention.
Hereinafter, the arrangement of an air meter according to a first embodiment of this invention will be explained using FIG. 1. The explanation is given by exemplifying a ratio-metric output type air meter.
A flow rate detecting circuit 3 comprises a heat generating resistor 1 positioned in an air flowing path, and a constant temperature controlling circuit 2. The heat generating resistor 1 receives a current from the constant temperature controlling circuit 2, and is heat-controlled by self heat generation. The constant temperature controlling circuit 2 detects an air flow rate from the magnitude of heat current by controlling the heat current to maintain the resistance of the heat generating resistor 1 to a predetermined value, and generates a flow rate detection signal V2.
An output characteristic adjusting circuit 4 adjusts the characteristic of the flow rate detection signal V2 by adjusting a zero point and an amplification factor on the basis of Equation (1), thereby to generate a flow rate characteristic signal V4 by adjusting the output signal of the air meter to a predetermined characteristic. In order to adjust the zero point of the output characteristic adjusting circuit 4, an internal reference voltage ES generated by a band gap reference power supply circuit 6 is used.