Patent Publication Number: US-6902318-B2

Title: Thermometer for engine of vehicle

Description:
TECHNICAL FIELD 
   The present invention relates to a thermometer for an engine of a vehicle that is optionally incorporated in a vehicle such as a racing two-wheel or four-wheel vehicle and that monitors the temperature of the engine so as to assist in driving the engine or driving a vehicle in an optimal state. 
   BACKGROUND ART 
   A thermometer that measures the incessantly changing temperature of an engine during running of a vehicle, digitizes the result of measurement, and displays the temperature is not incorporated in a racing two-wheel or four-wheel vehicle (including a cart). When it says that the temperature of an engine is measured, it signifies that the temperature of an engine main unit including cylinders is directly measured using a sensor. Otherwise, it signifies the measurement of the temperature of a radiator which cools cooling water heated by the engine or the measurement of the temperature of a cooling water flowing through a water pipe linking a water jacket, which encloses the cylinders, and the radiator. Otherwise, it signifies the measurement of the temperature of oil that is reserved in an oil pan located below the engine main unit and that flows through a circulation path. 
   By the way, managing the temperature of the engine during racing is very important in order to allow the engine to operate efficiently so as to attain a predetermined vehicle speed on a stable basis. Through the temperature management, occurrence of a fault such as the overheating of the engine or the seizure of a piston or a valve accompanying the overheating can be avoided. 
   Moreover, during racing, a transmission gear must be shifted based on the running speed of a vehicle or a road condition as well as an engine speed. A driver must perform this action by intuition. 
   However, a conventional two-wheel or four-wheel vehicle does not include a thermometer that indicates the incessantly changing temperature of an engine while measuring it. A driver must trust his/her intuition so as to accelerate the vehicle by stepping on an accelerator pedal or to shift a transmission gear by handling a shift level. Consequently, the performance of the engine may not be fully drawn out but the vehicle may be driven in a high-fuel consumption and high-noise condition. Moreover, when an engine speed is too high, that is, when the engine is overheated, if the transmission gear is shifted, a relatively small mechanical stress applied to the engine, a transmission, or a clutch may bring about a critical damage. 
   Accordingly, an object of the present invention is to provide a thermometer for an engine of a vehicle that is optionally incorporated in a vehicle such as an existing two-wheel or four-wheel vehicle, and that can readily measure and display the incessantly changing temperature of an engine during running of the vehicle. Thus, the vehicle can be driven in an optimal situation in which no stress is applied to the engine. When the measured temperature of the engine exceeds a set value, a warning indication is given so that, for example, an acceleration lever can be handled in order to restore the engine to an optimal driven state or restore the vehicle to an optimal driven state. 
   DISCLOSURE OF INVENTION 
   A thermometer for an engine of a vehicle in accordance with the present invention consists mainly of: a temperature/resistance element that is mounted on part of an engine incorporated in a vehicle and that detects the temperature of the engine as a change in resistance; a resistance-frequency converter that is optionally connected to the temperature/resistance element and converts the change in resistance into a change in frequency; a computer that calculates the temperature of the engine on the basis of an output of the resistance-frequency converter which represents the frequency and that displays the temperature on a display; and a key entry setting unit for use in setting a warning temperature of the engine to a value selected from among a plurality of predetermined values and thus determining the warning temperature. When the temperature of the engine exceeds the warning set temperature determined using the key entry setting unit, the computer instructs a temperature warning indicator to give a warning indication. Consequently, a driver discerns the incessantly changing temperature of the engine and whether the temperature of the engine has reached a set warning level. Thus, the driver can drive the vehicle with the engine retained in an optimal driven state. 
   A thermometer for an engine of a vehicle in accordance with another embodiment of the present invention includes: a battery voltage detecting unit that detects a voltage across a battery incorporated in a vehicle and converts the frequency of the voltage; and a voltage warning indicator that gives a warning indication when the voltage across the battery exceeds a pre-set warning set voltage. A computer calculates the voltage across the battery on the basis of a frequency represented by an output of the battery voltage detecting unit, and displays the calculated voltage across the battery on a display. When the voltage across the battery exceeds the warning set voltage determined using a key entry setting unit, the voltage warning indicator gives a warning indication. According to the embodiment, a driver immediately discerns whether the voltage across the battery and the incessantly changing temperature of the engine have reached a voltage of a set warning level and a temperature of a set warning level respectively. The driver can continue driving the vehicle with the engine retained in an optimal driven state. Moreover, occurrence of an error in a set value of the temperature of the engine derived from degradation in the quality of the battery can be prevented. 
   A thermometer for an engine of a vehicle in accordance with another embodiment of the present invention includes an engine speed detecting unit that detects an engine speed. A computer calculates the engine speed on the basis of an output of the engine speed detecting unit. When the calculated engine speed is equal to or larger than a shift timing point revolution speed and equal to or smaller than a shift timing warning set revolution speed, a shift timing point indicator is actuated. According to the present embodiment, a driver discerns the incessantly changing temperature of the engine and whether the temperature has reached a set warning level. Moreover, the present embodiment helps the driver grasp a shift timing point suitable for the engine speed. Consequently, driving the engine and driving a vehicle can be achieved efficiently according to a vehicle speed. 
   In a thermometer for an engine of a vehicle in accordance with another embodiment of the present invention, a computer has the ability to convert the temperature of an engine, which is obtained using a resistance-frequency converter, from a Celsius temperature to a Fahrenheit temperature or vice versa. Consequently, a driver of any nationality can discern the temperature of the engine so as to prevent overheating, and can thus drive the vehicle appropriately. 
   In a thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention, a warning temperature setting unit can be used to determine a warning temperature in either Celsius or Fahrenheit. Consequently, a driver of any nationality can recognize the warning temperature so as to prevent the overheating of the engine, and can thus drive a vehicle appropriately. 
   In a thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention, a battery voltage detecting unit includes a frequency division circuit that produces a signal whose frequency corresponds to an integral submultiple of the frequency into which the frequency of the voltage across a battery is converted and whose timing matches the data processing timing at which a computer processes data. Thus, the voltage across the battery detected in an analog form is converged into a signal that can be dealt with by the computer, and then immediately dealt with internally. 
   In a thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention, a key entry unit is realized with a key matrix unit. This is because the keys included in the key matrix unit can be used to determine a warning temperature, a warning voltage, and a setting of a timer, to store, display, or reset a maximum temperature of an engine, and to designate whether the functions of circuits are activated or inactivated automatically or manually at the time of starting or stopping the engine. Consequently, the key entry unit having a compact structure is used to designate and determine one mode or a plurality of modes relevant to the engine. 
   In a thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention, times measured during running of a vehicle are displayed on a display in stopwatch mode. In the stopwatch mode that is designated using a key entry unit, stopwatch measurement, lap time measurement, and split second measurement, or lap time/split second storage is carried out. Consequently, a racer can immediately discern the lap time or split second during driving, and easily check the vehicle speed per unit time. 
   A thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention includes a Celsius/Fahrenheit display setting unit that is used to specify in a computer whether the temperature of an engine obtained using a resistance-frequency converter is displayed on a display in either Celsius or Fahrenheit. Consequently, display in Celsius and display in Fahrenheit can be selectively achieved externally. 
   In a thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention, after an engine is stopped, when a set time has elapsed, a computer automatically halts the functions of all circuits except the function of a timer. Consequently, unnecessary power supply to the circuits during stoppage or suspension of driving can be ceased, and consumption of battery power can be minimized. 
   A thermometer for an engine of a vehicle in accordance with still another embodiment of the present invention includes a shift timing warning indicator that is driven when an engine speed detected by an engine speed detecting unit becomes equal to or higher than a shift timing warning set revolution speed determined using a key entry unit. Consequently, when the detected engine speed exceeds any of shift timing warning set revolution speeds determined in units of, for example, 100 rpm, shifting a transmission gear is avoided. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a thermometer for an engine of a vehicle in accordance with an embodiment of the present invention; 
       FIG. 2  is a perspective view of the thermometer for an engine of a vehicle shown in  FIG. 1 ; 
       FIG. 3  is a flowchart describing a flow of actions performed in the thermometer for an engine of a vehicle shown in  FIG. 1 ; 
       FIG. 4  is a flowchart describing a procedure of temperature measurement that is performed by the thermometer for an engine of a vehicle shown in  FIG. 1 ; 
       FIG. 5  is a flowchart describing a procedure of displaying that is performed by the thermometer for an engine of a vehicle shown in  FIG. 1 ; 
       FIG. 6  is a flowchart describing a procedure of temperature warning that is performed by the thermometer for an engine of a vehicle shown in  FIG. 1 ; 
       FIG. 7  is a block diagram showing a thermometer for an engine of a vehicle in accordance with another embodiment of the present invention; 
       FIG. 8  is a perspective view of the thermometer for an engine of a vehicle shown in  FIG. 7 ; 
       FIG. 9  is a flowchart describing a flow of actions that is performed by the thermometer for an engine of a vehicle shown in  FIG. 7 ; 
       FIG. 10  is a flowchart detailing a procedure of voltage measurement mentioned in  FIG. 9 ; 
       FIG. 11  is a flowchart detailing a procedure of SVD measurement mentioned in  FIG. 9 ; 
       FIG. 12  is a block diagram showing a thermometer for an engine of a vehicle in accordance with another embodiment of the present invention; and 
       FIG. 13  is a perspective view showing the thermometer for an engine of a vehicle shown in FIG.  12 . 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   For full details of the present invention, the present invention will be described in conjunction with the appended drawings. Referring to  FIG. 1 , a thermometer for an engine of a vehicle in accordance with an embodiment includes: a temperature/resistance element  11  such as a thermistor; a resistance-frequency converter  12  connected to the temperature/resistance element  11 ; a computer  13  having the resistance-frequency converter  12 ; a display  14  on which the temperature of an engine or the voltage across a battery is displayed; a warning temperature setting unit  15  serving as a key entry unit; and a temperature warning indicator  16 . 
   The temperature/resistance element  11  is mounted on part of the engine incorporated in a vehicle, and detects the temperature of the engine as a change in resistance. The resistance-frequency converter  12  converts a change in resistance detected by the temperature/resistance element  11  into a change in frequency which a computer to be described later can deal with. Moreover, the computer  13  calculates the temperature of the engine on the basis of a frequency represented by an output of the resistance-frequency converter  12 . The computer  13  then displays the calculated temperature on the display  14 . The computer  13  has the resistance-frequency converter  12  incorporated therein. 
   The warning temperature setting unit  15  is used to determine a warning temperature of the engine. The warning temperature is set to any value selected from among a plurality of predetermined values by inserting a jumper or by typing keys. When the temperature of the engine exceeds the warning set temperature determined by the warning temperature setting unit  15 , the temperature warning indicator  16  gives a warning indication by lighting a light-emitting diode or the like. 
   Moreover, the computer  13  converts the temperature of the engine obtained using the resistance-frequency converter  12  from a Celsius temperature to a Fahrenheit temperature or vice versa. Furthermore, the warning temperature setting unit  15  is designed so that the warning temperature can be determined in either Celsius or Fahrenheit. The warning temperature setting unit  15  includes, for example, three keys. Owing to the keys, the warning temperature in Celsius can be determined in four such manners that: the warning temperature is left undetermined; the warning temperature is set to 90° Celsius; the warning temperature is set to 100° Celsius; and the warning temperature is set to 120° Celsius. On the other hand, the warning temperature in Fahrenheit can be determined in four such manners that: the warning temperature is left undetermined; the warning temperature is set to 190° Fahrenheit, the warning temperature is set to 212° Fahrenheit, and the warning temperature is set to 250° Fahrenheit. 
     FIG. 2  is a perspective view showing the appearance of the thermometer for an engine of a vehicle that has the computer  13 , display  14 , warning temperature setting unit  15 , and temperature warning indicator  16  housed in a case  17 . Referring to  FIG. 2 , reference numeral  18  denotes a connector connected to the computer  13  over a lead. The connector  18  can be optionally coupled to a contact pin (not shown) included in the temperature/resistance element  11  mounted on part of the engine. Reference numerals  19  and  20  denote power terminals which are coupled to the positive and negative electrodes of the battery and through which power is supplied to the circuits including the computer  13  and being housed in the case  17 . 
   Next, typical temperature measurement to be performed by the foregoing thermometer for an engine of a vehicle will be described in conjunction with the flowchart of FIG.  3 . When a power switch (not shown) is turned on, various kinds of counters and registers are initialized automatically (step S 1 ). Thereafter, a main program is activated (step S 2 ). Moreover, a watchdog timer is repeatedly reset in order to detect an abnormality in the hardware of the computer  13  (step S 3 ). Thereafter, temperature measurement including calculation of the temperature of the engine in accordance with the present invention is executed (step S 4 ). The result of the measurement is displayed on the display (step S 5 ). 
   It is checked whether the temperature measurement is still in progress (step S 6 ). If the temperature measurement is still in progress, the watchdog timer is reset and the steps of measuring the temperature and of displaying data on the display are executed again. On the other hand, when the temperature measurement is completed, a timer interrupt is received in response to a request for an interrupt (step S 7 ). When the program is terminated, a halt instruction is issued (step S 8 ). The low power consumption mode is validated, and reception of an interrupt is inhibited (step S 9 ). The processing succeeding the step S 3  of resetting the watchdog timer is executed again. 
     FIG. 4  is a flowchart detailing the procedure of temperature measurement mentioned in FIG.  3 . Referring to  FIG. 4 , first, if temperature measurement using the temperature/resistance element  11  is executed, it is checked whether a temperature measurement flag is set (step S 11 ). If the temperature measurement flag is not set, it is checked if 2.5 sec has elapsed, that is, a 2.5 sec elapse flag is set (step S 12 ). When 2.5 sec has elapsed, the flag is reset (step S 13 ). The time of 2.5 sec is regarded as a temperature measurement interval. 
   Temperature measurement is then started. A temperature measurement-in-progress flag is set (step S 12 ). A counter incorporated in the computer  13  is set (step S 15 ). Thereafter, an interrupt factor flag incorporated in the resistance-frequency converter  12  is reset, and a state attained before the interrupt is restored (step S 16 ). The resistance-frequency converter is started acting (step S 17 ). Thereafter, the warning temperature setting unit  15  is used to determine a warning temperature set value that is applied to an input port (step S 18 ). It is then verified whether a warning temperature in Celsius has been measured (step S 19 ). If the warning temperature in Celsius has been measured, it is verified whether a warning temperature in Fahrenheit is measured, that is, a temperature being measured has reached the warning set temperature (step S 20 ). If the temperature being measured has reached the warning set temperature, warning is executed (step S 21 ). 
   If it is verified at step S 11  that the temperature measurement flag is set, it is checked if 0.45 sec has elapsed (step S 22 ). If 0.45 sec has elapsed, a time over flag and the temperature measurement-in-progress flag are reset (step S 23 ). The resistance-frequency converter  12  is stopped acting (step S 24 ). 
   Thereafter, warning temperature data listed in a table like the one shown in  FIG. 1  is specified using the counters incorporated in the computer  13  (step S 25 ). It is verified whether a measured temperature is higher or lower than the warning set temperature determined using the warning temperature setting unit  15  (step S 27  and step S 27 ). If the measured temperature is higher or lower, the warning temperature data is specified to represent the temperature (step S 29 ). Thereafter, step S 18  and subsequent steps are executed. If the measured temperature is neither higher nor lower, the temperature is converted into a hexadecimal form (step S 28 ). The step S 18  and subsequent steps are then executed. 
   If it is verified at step S 22  that 0.45 sec has not elapsed, it is checked whether temperature measurement is completed (step S 30 ). If the temperature measurement is completed, the temperature measurement-in-progress flag is reset (step S 31 ). It is then checked whether time base counting has come to an end (step S 32 ). If the time base counting has not come to an end, it is checked if measurement counting has come to an end (step S 33 ). If the measurement counting has not come to an end, step S 25  and subsequent steps are carried out. 
   If the time base counting or measurement counting has come to an end, end data is specified (step S 34 , step S 35 ). The step S 25  and subsequent steps are then carried out. If it is verified at step S 30  that temperature measurement is not completed, step S 18  and subsequent steps are carried out.  FIG. 5  is a flowchart detailing a procedure of displaying mentioned in FIG.  3 . Herein, whether temperature measurement data is displayed is determined (step S 41 ). Whether an indication signifying that a measured temperature is too high or low is displayed is indicated (step S 42 ). The indication is displayed when the measured temperature falls outside a predetermined range of measured temperature values. Thereafter, it is checked whether the indication signifying that the measured temperature is too high or low is displayed (step S 43 ). If the indication is not displayed, an indicated temperature is transmitted to a display buffer that is not shown (step S 44 ). The temperature is displayed with four digits on a seven-segment display (step S 45 ). 
   Incidentally, when it says that the indication signifying that the temperature is too high or low is displayed, it means that High or Low is displayed directly on the seven-segment display. Thereafter, it is checked if a temperature-too-high/low flag is set. If the flag is set, the display of degrees Celsius or Fahrenheit is deleted (step S 47 ), and a minus mark is deleted (step S 48 ). 
   If it is verified at step S 46  that the temperature-too-high/low flag is not set, it is checked whether the current temperature display mode is a Fahrenheit mode (step S 49 ). If the current mode is the Fahrenheit mode, a temperature is displayed in Fahrenheit (step S 51 ). The minus mark is displayed and deleted (step S 52 ). 
     FIG. 6  is a flowchart detailing a procedure of temperature warning mentioned in FIG.  4 . Referring to  FIG. 6 , first, it is checked whether a measured temperature-too-high flag is set (step S 61 ). If the temperature-too-high flag is set, a warning signal is applied to an output port (step S 62 ). If the temperature-too-high flag is not set, it is checked if a temperature-too-low flag is set (step S 63 ). If the temperature-too-low flag is set, the warning signal is not applied to the output port (step S 64 ). 
   If the temperature-too-low flag is not set, the measured temperature is compared with the warning set temperature (step S 65 ). It is then verified whether the measured temperature is lower than the warning set temperature (step S 66 ). If it is verified that the measured temperature is lower, the warning signal is not transmitted (step S 64 ). If the measured temperature is not lower, the warning signal is transmitted (step S 62 ). 
   As mentioned above, according to the present invention, the warning set temperature can be set to any of values that are different from one another in units of, for example, 1° Celsius. When the measured temperature of the engine detected using the temperature/resistance element exceeds the thus determined warning set temperature, the temperature warning indicator  16  gives a warning. This prompts a driver to drive a vehicle in a direction in which the engine temperature drops. Consequently, overheating of the engine can be avoided. In this case, the temperature of the engine can be measured in either Celsius or Fahrenheit. Moreover, the warning set temperature can be set to any value in Celsius or Fahrenheit. Consequently, a driver of any nationality can recognize the temperature of an engine so as to avoid overheating, and can therefore drive a vehicle appropriately. 
   Next, referring to  FIG. 7 , another embodiment of the present invention will be described. In  FIG. 7 , the same reference numerals are assigned to components identical to those shown in  FIG. 1. A  temperature/resistance element  11  is mounted on part of an engine incorporated in a vehicle, and detects the temperature of the engine as a change in resistance. A resistance-frequency converter  12  converts a change in resistance detected by the temperature/resistance element  11  into a change in frequency which a computer to be described later can deal with. The resistance-frequency converter  12  is incorporated in the computer, and optionally connected to the temperature/resistance element  11  using a lead or the like. 
   Moreover, the computer  13  calculates the temperature of the engine on the basis of a frequency represented by an output of the resistance-frequency converter  12 , and displays the temperature on a display  14 . Based on a detection signal produced by a battery voltage detecting unit  21  that will be described later, the computer  13  calculates a voltage across a power supply battery and displays it on the display  14 . 
   The battery voltage detecting unit  21  includes: a voltage/frequency converter  21   c  that converts the frequency of a terminal voltage of a battery  21   b  serving as an internal battery connected in series with a power switch  21   a ; and a frequency division circuit  21   d  that produces a signal whose frequency is an integral submultiple of the frequency represented by an output of the voltage/frequency converter  21   c  and which can be readily dealt with by the computer  13 . 
   The computer  13  works out either a Celsius or Fahrenheit temperature value on the basis of temperature data produced by the resistance-frequency converter  12 . Moreover, the computer  13  calculates the voltage across the battery on the basis of an output of the battery voltage detecting unit  2  that represents the detected voltage. Moreover, the computer  13  expresses the temperature of the engine in Celsius or Fahrenheit according to the settings of switches included in a Celsius/Fahrenheit temperature display setting unit  22 , and displays the temperature on the display  14 . 
   Furthermore, reference numeral  23  denotes a key matrix unit serving as a key entry unit. The key matrix unit is used to determine a warning temperature of the engine or a warning temperature of the battery, to store, display, or reset a maximum temperature, to determine the setting of a timer, or to designate that the functions of circuits other than the timer are automatically or manually halted in case the engine is stopped. The key matrix unit  23  has a plurality of key switches used to perform the above actions. Reference numeral  16  denotes a temperature warning indicator. When the temperature of the engine exceeds a warning set temperature determined using the key matrix unit  23 , the computer  13  instructs the temperature warning indicator  16  to give a warning indication.  FIG. 8  is a perspective view showing the thermometer for an engine of a vehicle having the circuit components, which include the computer  13 , display  14 , battery voltage detecting unit  21 , Celsius/Fahrenheit temperature display setting unit  22 , key matrix unit  23 , temperature warning indicator  16 , and voltage warning indicator  24 , housed in a case  25 . Referring to  FIG. 8 , reference numeral  26  denotes a connector connected to the computer  13  over a lead. The connector  26  can be optionally coupled to a contact pin (not shown) of the temperature/resistance element  11  mounted on part of the engine. Reference numeral  27  denotes a connector that is coupled to a power terminal through which power is supplied to the circuits including the computer  13  and being housed in the case  25 . The connector  27  is connected to the electrodes of the battery. 
   Next, typical actions to be performed mainly by the computer  13  shown in  FIG. 7  in the thermometer for an engine of a vehicle will be described in conjunction with the flowchart of FIG.  9 . When a power switch is turned on, various kinds of counters and registers are initialized (step S 71 ). Thereafter, a main program is activated (step S 72 ). After the main program is terminated, clock processing is performed, that is, a reference clock is generated based on an output of a timer incorporated in the computer  13 , and the number of clock pulses is counted (step S 73 ). 
   Furthermore, key entry is performed, that is, various data items are entered at the key matrix unit  23  that is a key entry unit in order to initiate data processing to be performed by the computer  13  (step S 74 ). First, engine temperature measurement in accordance with the present invention is executed (step S 75 ). Thereafter, voltage measurement and SVD measurement are executed for the battery  21   b  (step S 76  and step S 77 ). The results of the steps S 76  and S 77  are displayed by executing displaying (step S 78 ). When the program is terminated, halting is executed (step S 79 ). After the halting is completed (step S 80 ), step S 73  and subsequent steps are executed again. 
   Moreover, the procedures of temperature measurement, displaying, and temperature warning mentioned in  FIG. 9  are identical to those described in conjunction with  FIG. 4 ,  FIG. 5 , and FIG.  6 . Reiteration will be averted. 
     FIG. 10  is a flowchart detailing the procedure of voltage measurement performed by the computer  13 . Herein, when voltage measurement is executed, a voltage calculation flag is set (step S 81 ). A voltage is calculated based on an output of the battery voltage detecting unit  21  that represents a detected voltage (step S 82 ). It is checked if a voltage-too-low flag is set relative to the calculated voltage (step S 83 ). If the voltage-too-low flag is set, a high-level signal is applied to the input port. The computer  13  instructs the voltage warning indicator  24  to give a warning indication (step S 84 ). Thereafter, a voltage measurement-in-progress flag is reset and voltage measurement is terminated (step S 85 ). 
   On the other hand, if it is verified at step S 83  that the voltage-too-low flag is not set, it is checked if a voltage-too-high flag is set (step S 86 ). If the voltage-too-high flag is not set, it is checked if the measured voltage is equal to or lower than a pre-set value of 11.5 V (step S 87 ). If the measured voltage is equal to or lower than 11.5 V, step S 84  and subsequent steps are executed. In contrast, if the measured voltage is not equal to or lower than 11.5 V, a low-level signal is applied to the input port (step S 88 ). Thereafter, step S 85  is executed. Moreover, if it is found at step S 86  that the voltage-too-high flag is set, the low-level signal is immediately applied to the input port. Thereafter, the voltage measurement-in-progress flag is reset.  FIG. 11  is a flowchart detailing the procedure of SVD measurement to be performed by the computer  13 . During SVD measurement, for example, a voltage across a built-in lithium battery (3.0 V) is measured to see if the voltage had dropped to a set voltage (for example, 2.4 V, 2.5 V, 2.6 V, or 2.7 V). First, a request for measurement of the voltage across the built-in battery is issued to the computer  13  (step S 91 ). When the request is issued, an SVD measurement request flag is set (step S 92 ), and an SVD request input is set to 1 (step S 93 ). 
   Thereafter, when a predetermined time (200 μsec) has elapsed (step S 94 ), the SVD request input is reset to 0 (step S 95 ). Thereafter, it is checked if the result of SVD measurement is 1 (step S 96 ). If the result is 1, a battery voltage-lowered flag is set (step S 97 ). If the result is not 1, the battery voltage-lowered flag is reset and processing is terminated (step S 98 ). 
   Referring to  FIG. 12 , another embodiment of the present invention will be described below. In  FIG. 12 , the same reference numerals are assigned to the components identical to those shown in FIG.  1 . Reiteration will be averted.  FIG. 12  shows, in addition to the components shown in the block diagram of  FIG. 7 , an engine speed detecting unit  28  that detects an engine speed, a shift timing point indicator  29 , and a shift timing warning indicator  30 . Moreover, keys for use in determining a shift timing point revolution speed or a shift timing warning revolution speed are added to a key matrix unit  17 . 
   Consequently, when a driver uses the keys included in the key matrix unit  23  to determine the shift timing point revolution speed, if the computer  13  verifies that the engine is revolved at an engine speed equal to or higher than the shift timing point revolution speed and equal to or lower than the shift timing warning set revolution speed, the computer  13  lights or flickers the shift timing point indicator  29 . Consequently, a racer who is a driver may shift the transmission gear under an optimal condition at the timing of lighting or flickering the indicator. 
   Moreover, assume that the keys included in the key matrix unit  23  are used to determine the shift timing warning set revolution speed. In this case, when the engine speed reaches the shift timing warning set revolution speed, the computer  13  transmits a lighting signal to the shift timing warning indictor  30  so as to thus light or flicker the indicator. Consequently, the lighting or flickering of the shift timing warning indicator  30  enables a driver to recognize that shifting the transmission gear is inhibited. Breakage of a transmission or a clutch occurring when the transmission gear is forcibly shifted can be avoided. 
   Incidentally, the engine speed detecting unit  28  includes: an ignition noise detector  28   a  that detects an ignition noise occurring in the engine; and a wave reshaping circuit  28   b  that reshapes the wave of the ignition noise so as to thus convert it into a rectangular-wave pulsating signal, and transfers the pulsating signal to the computer  13 . Moreover, in the present embodiment, two temperature/resistance elements  11   a  and  11   b  are juxtaposed. Consequently, the temperature of the engine can be monitored at two places at the same time. This results in high-precision temperature detection. 
   Moreover, stopwatch measurement, lap time measurement, split second measurement, or lap time/split second storage can be designated arbitrarily using the keys included in the key matrix unit  23 . If necessary, an external operating member may be placed by the side of the operating keys included in the key matrix. In this case, the start or stop of stopwatch measurement or the like can be determined even during running of a vehicle. Furthermore, if an on-vehicle engine selecting switch is included in the key matrix unit  23 , a type of engine that is an object of measurement can be determined arbitrarily. 
   Moreover, a light guide plate that has a light-emitting diode as a light source, refracts light at right angles with respect to a direction of propagation in which light is propagated, and glows on a planar basis may be placed below a liquid crystal display panel. In this case, during running of a vehicle at night, the temperature of an engine, a voltage across a battery, and other display data can be clearly displayed on the liquid crystal display panel employed in the display  14  shown in  FIG. 1 ,  FIG. 7 , and FIG.  12 . 
     FIG. 13  is a perspective view of the thermometer shown in FIG.  12 . The two temperature/resistance elements  11   a  and  11   b , the computer  13 , the display  14 , the battery voltage detecting unit  21 , a Celsius/Fahrenheit temperature display setting unit  22 , the key matrix unit  23 , two temperature warning indicators  16   a  and  16   b , a voltage warning indicator  24 , the engine speed detecting unit  28 , the shift timing point indicator  29 , and the shift timing warning indicator  30  are housed in a case  31 . In the same drawing, reference numerals  32  and  33  denote connectors coupled to the computer  13  over leads. The connectors  32  and  33  can be optionally joined to the respective contact pins of the two temperature/resistance elements  11   a  and  11   b  mounted on part of the engine. 
   Reference numeral  34  denotes a connector having pins thereof connected to a power supply pin of a battery, through which power is supplied to the circuits housed in the case  31  and to an ignition circuit incorporated in the engine. Reference numerals  35  and  36  denote connectors to be connected to the operating keys included in the key matrix unit  23 . Reference numeral  37  denotes an antenna lead that serves as an integral part of the engine speed detecting unit  31 . The antenna lead  37  is used to detect an ignition noise, which occurs in the engine, on the basis of an electromagnetic induction. 
   Consequently, the computer  13  acquires temperature data concerning the engine from the temperature/resistance elements  11   a  and  11   b  via the connectors  32  and  33 . The computer  13  receives a supply voltage via the connector  34 . Moreover, the computer  13  receives an input entered using an external key via the connector  35  or  36 . 
   According to the present embodiment, as mentioned above, when the engine speed detected by the engine speed detecting unit  28  is equal to or lower than the shift timing warning set revolution speed and falls below the shift timing point revolution speed, the shift timing point indicator  29  indicates the fact. Consequently, a driver discerns that the transmission gear can be shifted. Moreover, when the detected engine speed exceeds the shift timing warning set revolution speed, the shift timing warning indicator  30  is lit. Consequently, the driver is inhibited to shift the transmission gear with the engine speed at this level. 
   INDUSTRIAL APPLICABILITY 
   As mentioned so far, a thermometer for an engine of a vehicle in accordance with the present invention is arbitrarily and optionally incorporated in an existing vehicle. Consequently, the thermometer helps a driver shift a transmission gear at the optimal shift timing or accelerate a vehicle while checking the temperature of an engine of the running vehicle. The thermometer hardly causes the engine to generate a noise, and is preferable for running of a vehicle with fuel consumption suppressed low.