Denso Corporation

Honda Giken Kogyo Kabushiki Kaisha

Nippon Soken, Inc.

Honda Giken Kogyo K.k.

Satoshi Hada

Eiichi Kurokawa

Toshiyuki Suzuki

Yoichi Sugimoto

Tomoo Kawase

Yoshihiro Urai

Shoji Ichikawa

Satoshi Haseda

Shohei Matsuda

Takahiro Eguchi

Katsuhide Akimoto

Mitsunobu Niwa

Toshiya Kanda

Keigo Mizutani

Akio Tanaka

Hirotoshi Inoue

Norio Suzuki

Yukihiro Yamashita

Satoshi Nakamura

Tomio Sugiyama

Shinichiro Imamura

Hirohiko Totsuka

Kazuhiro Okazaki

Shinya Teranishi

Kazuaki Fukami

Shoichiro Emmei

Takayuki Ishikawa

Keisuke Katsuta

Tetsuro Yamaguchi

Shouji Suzuki

A gas sensor control system for a gas sensor having a first, a second, and a third cell. The second cell produces a second cell electric current indicating the concentration of oxygen in gas in which the amount of oxygen has already been controlled by the first cell. The third cell produces a third cell electric current indicating the concentration of a preselected component of the gas in which the amount of oxygen has already been controlled by the first cell. A second cell circuit converts the second cell electric current into a voltage as a second cell current-measured value. A current adjuster produces a flow of an adjustment current as a function of the second cell current-measured value so that a third cell circuit converts the third cell electric current minus the adjustment current into a voltage as representing the concentration of the preselected component of the gas.

Gas sensor control system ensuring increased measurement accuracy

A gas sensor control device is disclosed as including a sensor cell having a negative terminal, to which a current-voltage converter is connected, and a differential amplifier is connected to the current-voltage converter to provide a current measured result applied to a microcomputer. The current-voltage converter has an opposite-to-sensor terminal to which another differential amplifier is connected. A sensor-side terminal of the current-voltage converter and another differential amplifier is electrically connected to each other via an electric pathway having a sensor-current flow disabling pathway in which a switch circuit is provided. Closing the switch circuit allows a potential difference between both terminals of the current-voltage converter is zeroed. With the switch circuit closed, the microcomputer calculates an element current correcting value, while detecting an electromotive force of the sensor cell based on which a failure is determined.

Gas sensor control device

A gas concentration measuring apparatus for use in air-fuel ratio control of automotive engines is designed to determine the concentration of oxygen within a wide and a narrow range using a sensor current flowing through a sensor element. The apparatus includes an amplifier circuit equipped with an operational amplifier and a plurality of amplifying resistors and a switch. The switch is responsive to a request signal to switch a relation in electrical connection between an operational amplifier and the amplifying resistors to distribute the amplifying resistors into an input resistor and a feedback resistor for the operational amplifier to change an amplification factor of the amplifier circuit. This results in a change in resolution of measurement of the concentration of oxygen, thereby ensuring enhanced accuracy in determining the concentration of oxygen in a selected one of the narrow and wide ranges.

Gas concentration measuring apparatus designed to enhance measurement accuracy in desired range

In a gas concentration detecting apparatus, a voltage is applied to electrodes of a sensor element. A change is caused in either the applied voltage or an element current. An amount of a change in each of a current value and a voltage value caused is measured in response to the caused change. An amount of resistance of the sensor element is calculated based on a ratio between the change amounts in the current value and the voltage value. A detection unit detects abnormality relating to controlling the sensor by utilizing at least one of the change amounts in the current value and the voltage value.

Gas concentration detecting apparatus

A noiseless circuit structure of a gas concentration measuring apparatus is provided. The gas concentration measuring apparatus includes a control circuit and a gas sensor including a solid electrolyte body, a cell, and a heater serving to heat the solid electrolyte body up to an activation temperature. The control circuit is designed to cancel or remove electric noises arising from an on-off operation of the heater added to a sensor output.

Noiseless gas concentration measurement apparatus

An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converterto an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPFis input to a bias control circuit. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuitto thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Control method for gas concentration sensor

A heater control system is provided for controlling the temperature of a heater used to heat a solid electrolyte-made sensor element of a gas concentration sensor up to a given temperature at which the sensor element is activated to provide a correct gas concentration output for controlling a preselected variable used in, for example, an automotive air-fuel ratio control system. The heater control system measures a resistance value of the sensor element and controls an electric power supplied to the heater as a function of the resistance value. The heater control system is designed to determine a controlled variable properly used to control the heater, thereby resulting in improved controllability of a power supply to the heater and also works to minimize an error in determining the resistance of the heater.

Power supply control system for heater used in gas sensor

A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of Oand HOcontained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of Oand NOinto a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

Gas concentration measuring apparatus designed to minimize error component contained in output

A heater control apparatus used for a gas concentration sensor heats a sensor element including a solid electrolyte body up to a desired activation temperature. The heater control apparatus determines an actual resistance value of the sensor element, controls a power supply to the heater as a function of a difference between the actual resistance value and a target one, determines a power supplied to the heater, and determines a reference resistance value of the sensor element based on a predetermined fundamental relation between a power used in the heater and a resistance value of the sensor element to correct the target resistance value as a function of a difference between the reference resistance value and the actual resistance value.

A gas concentration measuring apparatus is provided which includes a gas concentration sensor consisting of a pump cell, a sensor cell, and a monitor cell. The pump cell works to determine the concentration of O . The sensor cell works to decompose an oxygen containing gas such as NOx and provide an output indicative of the concentration of NOx. The apparatus also includes an applying voltage determining circuit which looks up a predetermined voltage-to-current relation to determine a target voltage to be applied to the pump cell as a function of the current produced by the pump cell so as to preclude the pump cell from decomposing the oxygen containing gas component, thereby minimizing an error in determining the concentration of oxygen containing gas as a function of the output of the sensor cell.

Gas concentration measuring apparatus compensating for error component of output signal

An air-fuel ratio sensor is equipped with a sensing element including a solid electrolytic substrate. When the sending element is warmed up and activated by a heater, a microcomputer controls electric power supplied to the heater based on a control base value being set according to a duty ratio&equals;100%. A power profile P is determined beforehand to set a target heater power. Through the warm-up heater power control, an actual heater power supplied to the heater is equalized to the target heater power determined according to the power profile P

Heater control apparatus for a gas concentration sensor

A heater power supply control system is provided for controlling the temperature of a heater used to heat a solid electrolyte-made sensor element of a gas concentration sensor up to a desired activation temperature. The heater power supply control system measures a resistance value of the sensor element and controls an electric power supply to the heater using a PI control function. The heater power supply control system works to limit the value of an integral term of the PI control function in the course of activation of the sensor element, thereby avoiding overshoot of the resistance value of the sensor element, which avoids thermal damage of the sensor element.

A braking apparatus for vehicles BU, in which plurality systems of individually separated brake fluid pressure passages BC(A), BC(B) are arranged, and each passage is provided with at least one brake fluid pressure retaining means RU(A), RU(B) for continuously retaining brake fluid pressure within a wheel cylinder WC(A), WC(B) arranged in the brake fluid pressure passage after a depression of a brake pedal BP is released and for releasing the retained brake fluid pressure in response to an increase of a starting driving force of the vehicle, wherein the release of the retained brake fluid pressure is carried out in a time differential manner at each brake fluid pressure retaining means.

Braking apparatus for vehicles

A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of O and HOx contained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of O and HOx into a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

A limit-current type A/F sensor produces element current responsive to oxygen concentration in the exhaust gas when a voltage is applied to its sensor element portion. An application voltage control circuit comprises an operational amplifier and resistors. An output of the control circuit is applied to one terminal of the A/F sensor via a driver circuit. The other terminal of the A/F sensor is connected to an output terminal of an operational amplifier via a current-detecting resistor. The element current value, detected by the current-detecting resistor, is returned to the application voltage control circuit via a buffer. In the application voltage control circuit, adjustment of the gain is performed in such a manner that the inclination of the application voltage line on the V-I coordinate becomes larger than the inclination equivalent to the A.C. impedance of the sensor element in the sensor activated condition.

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Kariya, Japan

Satoshi Hada