关于数据库的问题！！objAdap.Fill(objDSet, strSql)出错。

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        Dim Zhijin As String
        Zhijin = ""
        Zhijin = ComboBox1.Text
        Dim strConn As String = "Provider = Microsoft.Jet.OLEDB.4.0;Data Source = 铁心参数.mdb"
        Dim objConn As New OleDbConnection(strConn)
        objConn.Open()
        Dim strSql = "Select * From 表1 where 铁心直径 = " + Zhijin

        Dim objAdap As New OleDbDataAdapter(strSql, objConn)
        objConn.Close()
        Dim objDSet As New DataSet
        objAdap.Fill(objDSet, strSql)
      
        TextBox1.Text = objDSet.Tables(0).Rows(0)("第1级片宽")
        TextBox2.Text = objDSet.Tables(0).Rows(0)("第2级片宽")
      
        TextBox8.Text = objDSet.Tables(0).Rows(0)("第1级叠厚")
        TextBox9.Text = objDSet.Tables(0).Rows(0)("第2级叠厚")
        
End Sub

当关闭窗口时出现错误，在objAdap.Fill(objDSet, strSql)这一句标成黄色，说是未处理OleDbException，语法错误 (操作符丢失) 在查询表达式 '铁心直径 =' 中。
这种问题怎么解决？   （用VB.ENT编程）