JP4106339B2 - Production method of fuel injection pump - Google Patents

Description

The present invention relates to a structure of a distribution type fuel injection pump, and more particularly to a technique for assuring the accuracy of a sliding surface such as a plunger barrel.

  In the conventional fuel injection pump in which the plunger is moved up and down within the plunger barrel, the plunger barrel is coupled to the hydraulic head by shrink fitting. The production process of the hydraulic head related to this shrink fitting is, for example, as shown in FIG. 5, and the plunger barrel after the heat treatment is shrink fitted to the hydraulic head in a specified temperature range. After the shrink fitting, the inside of the plunger barrel, that is, the plunger sliding surface is honed. This honing ensures the accuracy of the plunger sliding surface and prevents the plunger from being seized. Further, in the distribution type fuel injection pump, like the plunger barrel, the distribution shaft sleeve is shrink-fitted and coupled to the hydraulic head, and the distribution shaft is seized by honing the inside of the distribution shaft sleeve. Is prevented from occurring. The structure of the above hydraulic head is known (for example, refer to Patent Document 1). Moreover, it can be said that these techniques related to shrink fitting and honing are well-known techniques.

JP 2003-106240 A

However, the process shown in FIG. 5 has the following problems.
That is, when the plunger barrel and the distribution shaft sleeve are shrink-fitted, residual stress is generated between these and the hydraulic head shrink-fit surfaces M3 and M4 (see FIG. 6). This adversely affects the accuracy of the sliding surfaces of the plunger barrel and the distribution shaft sleeve. FIG. 6 compares the measurement results of the surface heights G3 and G4 of the sliding surfaces S3 and S4 immediately after the honing and the surface heights L3 and L4 of the sliding surfaces S3 and S4 after several hours after the honing. It is shown, and it has been confirmed that the height of the sliding surface changes greatly with the passage of time. That is, even if the sliding surfaces S3 and S4 are processed with high accuracy by honing, the accuracy is impaired with the passage of time.

  In this way, if the accuracy obtained by honing is not maintained, wear between the plunger and the plunger barrel, wear between the distribution shaft and the distribution shaft sleeve, and further problems such as seizure occur. It will lead to. In addition, since the high pressure fuel is present, the fuel pressure may adversely affect the accuracy of the sliding surface in combination with the residual stress.

  In view of the above problems, the present invention proposes a technique for guaranteeing the accuracy of the sliding surfaces of the plunger and the distribution shaft by reducing the residual stress generated on the shrink-fit surface.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

A method for producing a fuel injection pump, wherein a plunger barrel (2), which is a cylindrical member having a cylinder part, and a distribution shaft sleeve (3) are shrink-fitted and coupled to a hydraulic head (1). A first step of shrink fitting the plunger barrel (2) and the distribution shaft sleeve (3), which are shaped members, to the heated hydraulic head (1), and a heating furnace such as an electric furnace after the first step A second step of performing a tempering process for heating and cooling the plunger barrel (2), the distribution shaft sleeve (3) and the hydraulic head (1) after shrink fitting , A third step of honing the sliding surface of the cylinder portion later, and for the second step of performing the tempering process, an upper limit value of a temperature zone (T2) set in the tempering process is defined as a cylindrical shape Shrink fitting In the first step, it is to substantially the same as the upper limit of the temperature zone defined at the time (T1) for heating the hydraulic head (1).

  As effects of the present invention, the following effects can be obtained.

A method for producing a fuel injection pump, wherein a plunger barrel (2), which is a cylindrical member having a cylinder part, and a distribution shaft sleeve (3) are shrink-fitted and coupled to a hydraulic head (1). A first step of shrink fitting the plunger barrel (2) and the distribution shaft sleeve (3), which are shaped members, to the heated hydraulic head (1), and a heating furnace such as an electric furnace after the first step A second step of performing a tempering process for heating and cooling the plunger barrel (2), the distribution shaft sleeve (3) and the hydraulic head (1) after shrink fitting , A third step of honing the sliding surface of the cylinder portion later, and for the second step of performing the tempering process, an upper limit value of a temperature zone (T2) set in the tempering process is defined as a cylindrical shape Shrink fitting In the first step, since substantially the same as the upper limit of the temperature zone (T1) of a prescribed time to heat the hydraulic head (1), the accuracy of the sliding surface is ensured also after long Thus, it is possible to prevent the friction between the sliding surface of the cylinder part and the plunger, the distribution shaft, etc., and to prevent wear of these members. In addition, seizure of the member on the sliding surface can be prevented. Moreover, the internal distortion of the hydraulic head is removed by the tempering process, thereby stabilizing the quality.

Further, by setting the upper limit value of the temperature zone T2 set in the tempering process to be substantially the same as the upper limit value of the temperature zone T1 set in the shrink fitting of the first step for the second step, the cylinder portion The decrease in the surface hardness of the sliding surfaces S1 and S2 of 2a is suppressed within an allowable range.
That is, when the tempering process is performed at a high temperature in the second step, the surface hardness of the sliding surfaces S1 and S2 (see FIG. 3) of the cylinder part 2a is lowered. The amount of decrease in the surface hardness increases as the temperature of the tempering process increases. For this reason, it is necessary to define the upper limit value of the temperature zone set when performing the temper process to a temperature that does not become high. Further, since the deflector 2d (see FIG. 1) is also in a shrink-fitted state, it is necessary to prevent the hardness of the deflector 2d from being lowered and to prevent the deflector 2d from being eroded by spill pressure. The optimal setting is required.
Therefore, in the present invention, for the second step, the upper limit value of the temperature zone T2 set in the temper process is made substantially the same as the upper limit value of the temperature zone T1 set in the shrink fitting of the first step. As a result, the decrease in the surface hardness of the sliding surfaces S1 and S2 of the cylinder portion 2a can be suppressed within an allowable range without becoming high temperature.
That is, by setting the upper limit value of the temperature zone T2, the surface hardness higher than the lower limit value F1 of the set surface hardness can be realized on the sliding surfaces S1 and S2 of the cylinder portion 2a. In this way, by keeping the decrease in the surface hardness within an allowable range, it is possible to prevent the plunger barrel 2 and the distribution shaft sleeve 3 from being worn and the occurrence of seizure on the sliding surface.

To reduce the residual stress generated on the shrink-fit surface and to guarantee the accuracy of the sliding surface of the plunger and distribution shaft, a tubular member having a cylinder part is shrink-fitted to the hydraulic head. A plunger barrel (2), which is a cylindrical member having the cylinder portion, and a distribution shaft sleeve (3) are shrink-fitted and coupled to a hydraulic head (1). A fuel injection pump production method comprising: a first step of shrink fitting the plunger barrel (2) and the distribution shaft sleeve (3), which are the cylindrical members, to the heated hydraulic head (1); Temper for heating and cooling the plunger barrel (2), distribution shaft sleeve (3), and hydraulic head (1) after shrink fitting in a heating furnace such as an electric furnace after the first step. A second step of performing a physical, comprising a third step of honing the sliding surface of the cylinder portion after said second step, a, a second step of performing said tempering, the tempering The upper limit value of the set temperature zone (T2) is substantially the same as the upper limit value of the specified temperature zone (T1) when the hydraulic head (1) is heated in the first step of shrink fitting the cylindrical member. The production method is the same.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a hydraulic head 1 of a fuel injection pump according to the present invention.

  In the configuration shown in FIG. 1, the plunger head 2 and the distribution shaft sleeve 3 are shrink-fitted to the hydraulic head 1. A plunger 4 is inserted into the cylinder portion 2a of the plunger barrel 2 so as to be slidable up and down. An annular fuel gallery 2b is formed on the outer periphery of the plunger barrel 2, and a spill port 2c is formed from the fuel gallery 2b into the cylinder portion 2a. The cylinder portion passes through the spill port 2c. Fuel is supplied and discharged between 2a and the fuel gallery 2b. In the plunger barrel 2, a deflector 2 d is provided at a position corresponding to the spill port 2 c in order to prevent the spill pressure (discharge pressure) of the high-pressure fuel from directly acting on the hydraulic head 1. A distribution shaft 5 is rotatably inserted into the cylinder portion 3 a inside the distribution shaft sleeve 3.

FIG. 2 shows a process particularly related to the present invention regarding the production process of the hydraulic head 1. That is, a method for producing a fuel injection pump in which a cylindrical member having a cylinder portion such as a plunger barrel 2 or a distribution shaft sleeve 3 is shrink-fitted and coupled to a hydraulic head 1, wherein the tubular member is shrink-fitted. A first step of performing a temper treatment after the first step , a third step of honing the sliding surfaces of the cylinder portions 2a and 3a after the second step, It is set as the production method which comprises.

  In the first step, for example, a tubular member such as the plunger barrel 2 is shrink-fitted onto the hydraulic head 1 in a specified temperature zone T1 by a shrink-fitting device. In the fuel injection pump in which the plunger barrel 2 and the distribution shaft sleeve 3 are separately formed as shown in FIG. 1 (relatively small), the area of the shrink-fitting surfaces M1 and M2 (see FIG. 3) is small. Therefore, the lower limit value of the prescribed temperature zone T1 is set to a value that can secure the binding force by shrink fitting. For example, in the configuration shown in FIG. 1, when the hydraulic head 1 and the cylindrical member are made of alloy tool steel (SKD11), the temperature zone T1 is set to 250 ° C. to 270 ° C., and so on. In addition, the temperature zone T1 is set according to the area of the shrink-fit surface and the material of the tubular member.

Next, in the second step, tempering is performed by a heating furnace (for example, an electric furnace). This temper treatment is a kind of heat treatment. By this tempering treatment, residual stress generated on the shrink-fitting surfaces M1 and M2 (see FIG. 3) between the hydraulic head 1 and the tubular member can be removed.

  Next, in the third step, the sliding surface of the cylinder part 2a of the cylindrical member is honed by a honing machine. Here, the prescribed roundness is achieved by honing the sliding surface. And when this honing is performed, the temper treatment is performed in the second step and the residual stress is removed, so that the roundness immediately after the honing is maintained even after a long time has passed. become. That is, the accuracy of the sliding surface can be guaranteed even after a long time has passed.

  FIG. 3 shows the surface of the sliding surfaces S1 and S2 after several hours from the surface heights G1 and G2 of the sliding surfaces S1 and S2 measured immediately after honing for the fuel injection pump produced by the above process. It shows that the heights L1 and L2 do not change greatly. This is because the residual stress generated on the shrink-fitting surfaces M1 and M2 has been removed by the temper treatment in the second step. The applicant of the present application has shown that the amount of change in the surface height can be suppressed to about one-twentieth as compared with the maximum amount of change, as compared with a conventional production method that does not perform tempering. This is confirmed (see FIG. 4 and FIG. 6 for comparison). In this way, since the accuracy of the sliding surface is ensured even after a long time has elapsed, the occurrence of friction between the sliding surface and the plunger 4 or the distribution shaft 5 can be prevented. Can be prevented, and seizure of the member on the sliding surface can be prevented. Further, the internal distortion of the hydraulic head is removed by the tempering process, thereby stabilizing the quality.

  As shown in FIG. 4, when the temper process is performed in the second step, the surface hardness of the sliding surfaces S1 and S2 (see FIG. 3) of the cylinder part 2a is lowered. The amount of decrease in the surface hardness increases as the temperature of the tempering process increases. For this reason, it becomes necessary to define the upper limit value of the temperature range set when performing the temper process. In addition, since the deflector 2d (see FIG. 1) is in a shrink-fitted state, it is necessary to prevent a decrease in hardness of the deflector 2d and to prevent erosion of the deflector 2d due to spill pressure. The optimal setting is required. Therefore, in this embodiment, for the second step, the upper limit value of the temperature zone T2 set in the temper process is substantially the same as the upper limit value of the temperature zone T1 set in the shrink fitting of the first step. By doing so, the decrease in the surface hardness of the sliding surfaces S1 and S2 of the cylinder portion 2a is suppressed within an allowable range. That is, by setting the upper limit value of the temperature zone T2, the surface hardness higher than the lower limit value F1 of the set surface hardness can be realized on the sliding surfaces S1 and S2 of the cylinder portion 2a. In this way, by keeping the decrease in surface hardness within an allowable range, it is possible to prevent wear of the plunger barrel 2 and the distribution shaft sleeve 3 and occurrence of seizure on the sliding surface.

The present invention can be applied to a distribution type fuel injection pump provided with a plunger barrel and a distribution shaft sleeve, in which a drive system component in a cam chamber is lubricated by engine lubricating oil.

It is side surface sectional drawing which shows the structural example of the hydraulic head of the fuel injection pump to which this invention is applied. It is a block diagram shown about the production process of the fuel injection pump concerning this invention. It is explanatory drawing about the surface height of a sliding face. It is explanatory drawing about the setting of surface hardness. It is a block diagram shown about the production process of the conventional fuel injection pump. It is explanatory drawing which shows that the precision of a sliding surface is not guaranteed in the conventional production process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic head 2 Plunger barrel 2a Cylinder part 3 Distribution shaft sleeve S1 Sliding surface S2 Sliding surface

Claims (1)

A method for producing a fuel injection pump, wherein a plunger barrel (2), which is a cylindrical member having a cylinder part, and a distribution shaft sleeve (3) are shrink-fitted and coupled to a hydraulic head (1). A first step of shrink fitting the plunger barrel (2) and the distribution shaft sleeve (3), which are shaped members, to the heated hydraulic head (1), and a heating furnace such as an electric furnace after the first step A second step of performing a tempering process for heating and cooling the plunger barrel (2), the distribution shaft sleeve (3) and the hydraulic head (1) after shrink fitting , A third step of honing the sliding surface of the cylinder portion later, and for a second step of performing the tempering process, an upper limit value of a temperature zone (T2) set in the tempering process is defined as a cylindrical shape Shrink fitting In the first step, the upper limit value and to substantially the same method of producing the fuel injection pump, wherein the temperature zones (T1) of a prescribed time to heat the hydraulic head (1).

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